Abdul hafeez kalsekar -- OCS/OCE/OCP

Saturday, September 14, 2024

Oracle 19c New Feature High-Frequency Statistics : No more stale statistics in 19c

Since there was lot of hype of 19c new feature High frequency statistics thought of documenting few note .

Since main motto of Blog is High-Frequency Statistics have mentioned about it first But later also documented notes on our routine stats maintenance window

#########################

19c High-frequency automatic optimizer statistics collection. :

#########################

The new feature introduced in Oracle 19c called High-Frequency Automatic Optimizer Statistics Collection complements the standard automatic statistics collection job.

AutoTask schedules tasks to run automatically between maintenance windows. By default, one window is scheduled for each day of the week. Automatic optimizer statistics collection (DBMS_STATS) runs in all predefined maintenance windows.

Statistics can go stale between two consecutive statistics collection tasks. If data changes frequently, the stale statistics could cause performance problems. For example, a brokerage company might receive tremendous data during trading hours, leading the optimizer to use stale statistics for queries executed during this period.

By default, the high-frequency statistics collection occurs every 15 minutes and as such there is less possibility of having stale statistics even for those tables where data is changing continuously.

The DBMS_STATS.SET_GLOBAL_PREFS procedure is used to enable and disable the high-frequency statistics gather task as well as change the execution interval (default 15 minutes) and the maximum run time (60 minutes).

select

s.START_TIME, s.END_TIME

,s.STALENESS

,s.OSIZE

,s.OBJ#, name, NVL(subname,'<NULL>') subname

,s.TYPE#

,decode(s.type#, 0, 'NEXT OBJECT', 1, 'INDEX', 2, 'TABLE', 3, 'CLUSTER',

19, 'TABLE PARTITION', 20, 'INDEX PARTITION',

34, 'TABLE SUBPARTITION', 35, 'INDEX SUBPARTITION',

'UNDEFINED') object_type

,s.FLAGS, s.STATUS

,s.SID, s.SERIAL#

,s.PART#, s.BO#

from sys.stats_target$ s

left outer join sys.obj$ o on o.obj# = s.obj#

Where start_time >= sysdate-10/1440

order by start_time

==> To Change Setting

EXEC DBMS_STATS.SET_GLOBAL_PREFS('AUTO_TASK_STATUS','ON');

EXEC DBMS_STATS.SET_GLOBAL_PREFS('AUTO_TASK_MAX_RUN_TIME','600');

EXEC DBMS_STATS.SET_GLOBAL_PREFS('AUTO_TASK_INTERVAL','240');

==> to check current setting

SET LINESIZE 100 pages 99

COLUMN auto_task_status HEADING 'Auto Task|Status' FORMAT a10

COLUMN auto_task_max_run_time HEADING 'Auto Task|Max Run Time' FORMAT a15

COLUMN auto_task_interval HEADING 'Auto Task|Interval' FORMAT a10

SELECT DBMS_STATS.GET_PREFS('AUTO_TASK_STATUS') AS auto_task_status

, DBMS_STATS.GET_PREFS('AUTO_TASK_MAX_RUN_TIME') AS auto_task_max_run_time

, DBMS_STATS.GET_PREFS('AUTO_TASK_INTERVAL') AS auto_task_interval

FROM dual;

==> To Check execution history

COL OPID FORMAT 99999999

COL STATUS FORMAT a11

COL ORIGIN FORMAT a20

COL COMPLETED FORMAT 99999

COL FAILED FORMAT 99999

COL TIMEOUT FORMAT 99999

COL INPROG FORMAT 99999

SELECT OPID, ORIGIN, STATUS, TO_CHAR(START_TIME, 'DD/MM HH24:MI:SS' ) AS BEGIN_TIME,

TO_CHAR(END_TIME, 'DD/MM HH24:MI:SS') AS END_TIME, COMPLETED, FAILED,

TIMED_OUT AS TIMEOUT, IN_PROGRESS AS INPROG

FROM DBA_AUTO_STAT_EXECUTIONS

ORDER BY OPID;

with x as (

SELECT x.*

, end_time-start_time diff

, start_time-(LAG(end_time,1) over (order by start_time)) start_lag

FROM DBA_AUTO_STAT_EXECUTIONS x

ORDER BY x.start_time

)

select opid, origin, status

, ((extract( day from start_lag )*24+

extract( hour from start_lag ))*60+

extract( minute from start_lag ))*60+

extract( second from start_lag ) start_lag

, start_time, end_time

, ((extract( day from diff )*24+

extract( hour from diff ))*60+

extract( minute from diff ))*60+

extract( second from diff ) secs

, completed, failed, timed_out, in_progress

from x

Where start_time >= sysdate-1/24

#########################

To Enable Or Disable old Auto task during daily maintenance window

#########################

BEGIN

DBMS_AUTO_TASK_ADMIN.ENABLE (

client_name => 'auto optimizer stats collection'

, operation => NULL

, window_name => NULL

);

END;

BEGIN

DBMS_AUTO_TASK_ADMIN.DISABLE (

client_name => 'auto optimizer stats collection'

, operation => NULL

, window_name => NULL

);

END;

-- disable sql tuning advisor on monday

BEGIN

dbms_auto_task_admin.disable(

client_name => 'sql tuning advisor',

operation => NULL,

window_name => 'MONDAY_WINDOW');

END;

#########################

Alter old auto stats setting for daily maintenance window

#########################

EXEC DBMS_STATS.alter_stats_history_retention(90);

EXEC DBMS_STATS.set_global_prefs('estimate_percent', '5');

BEGIN

DBMS_SQLTUNE.set_tuning_task_parameter('SYS_AUTO_SQL_TUNING_TASK', 'LOCAL_TIME_LIMIT', 1200);

DBMS_SQLTUNE.set_tuning_task_parameter('SYS_AUTO_SQL_TUNING_TASK', 'ACCEPT_SQL_PROFILES', 'FALSE');

DBMS_SQLTUNE.set_tuning_task_parameter('SYS_AUTO_SQL_TUNING_TASK', 'MAX_SQL_PROFILES_PER_EXEC', 20);

DBMS_SQLTUNE.set_tuning_task_parameter('SYS_AUTO_SQL_TUNING_TASK', 'MAX_AUTO_SQL_PROFILES', 10000);

END;

#########################

Old Auto Task Details View for daily maintenance window :

#########################

select log_id,owner,job_name,status,actual_start_date,instance_id from dba_scheduler_job_run_details

where job_name = 'GATHER_STATS_JOB' and ACTUAL_START_DATE>SYSDATE-3

or job_name like 'ORA$AT_OS_OPT_SY%' and ACTUAL_START_DATE>SYSDATE-3

order by log_date desc;

COL CLIENT_NAME FORMAT a31

select client_name, status, window_group from dba_autotask_client;

SELECT client_name, status FROM dba_autotask_operation;

SELECT task_name, status, TO_CHAR(execution_end,'DD-MON-YY HH24:MI')

FROM dba_advisor_executions WHERE task_name='SYS_AUTO_SQL_TUNING_TASK'

ORDER BY execution_end;

SELECT WINDOW_NAME, to_char(START_TIME,'DD-Mon-RR hh24:mi') START_TIME, DURATION

FROM DBA_AUTOTASK_SCHEDULE

ORDER BY WINDOW_NAME, START_TIME DESC;

select client_name,JOB_NAME,JOB_STATUS,JOB_START_TIME,JOB_DURATION from DBA_AUTOTASK_JOB_HISTORY

where JOB_START_TIME >systimestamp -7 and client_name='auto optimizer stats collection' order by 4 desc ;

select parameter_name, parameter_value

from dba_advisor_parameters

where task_name = 'SYS_AUTO_SQL_TUNING_TASK'

and parameter_name IN ('ACCEPT_SQL_PROFILES',

'MAX_SQL_PROFILES_PER_EXEC',

'MAX_AUTO_SQL_PROFILES');

select window_name, repeat_interval, duration from dba_scheduler_windows where window_name like 'WEEK%';

select window_name, next_start_date , enabled , resource_plan from dba_scheduler_windows ;

SELECT window_name,TO_CHAR(window_next_time,'DD-MON-YY HH24:MI:SS')

,sql_tune_advisor, optimizer_stats, segment_advisor

FROM dba_autotask_window_clients;

select * from dba_scheduler_wingroup_members order by 1,2;

col target for a20

col start_time for a20

col end_time for a20

col notes for a20

select target,start_time,end_time,notes

from DBA_OPTSTAT_OPERATION_TASKS

-- where target like '%DEMO%'

order by OPID desc;

set linesize 250

set pagesize 100

column preference_name format a30

column preference_value format a50

-- global preferences

with preflist (preference_name,global_only)

as (select 'APPROXIMATE_NDV_ALGORITHM',0 from dual union all

select 'AUTO_STAT_EXTENSIONS' ,0 from dual union all

select 'AUTO_TASK_STATUS' ,0 from dual union all

select 'AUTO_TASK_MAX_RUN_TIME' ,0 from dual union all

select 'AUTO_TASK_INTERVAL' ,0 from dual union all

select 'AUTOSTATS_TARGET' ,1 from dual union all

select 'CASCADE' ,0 from dual union all

select 'CONCURRENT' ,0 from dual union all

select 'DEGREE' ,0 from dual union all

select 'ESTIMATE_PERCENT' ,0 from dual union all

select 'GLOBAL_TEMP_TABLE_STATS' ,0 from dual union all

select 'GRANULARITY' ,0 from dual union all

select 'INCREMENTAL' ,0 from dual union all

select 'INCREMENTAL_STALENESS' ,0 from dual union all

select 'INCREMENTAL_LEVEL' ,0 from dual union all

select 'METHOD_OPT' ,0 from dual union all

select 'NO_INVALIDATE' ,0 from dual union all

select 'OPTIONS' ,0 from dual union all

select 'PREFERENCE_OVERRIDES_PARAMETER',0 from dual union all

select 'PUBLISH' ,0 from dual union all

select 'STALE_PERCENT' ,0 from dual union all

select 'STAT_CATEGORY' ,0 from dual union all

select 'TABLE_CACHED_BLOCKS' ,0 from dual union all

select 'WAIT_TIME_TO_UPDATE_STATS',0 from dual )

select preference_name,

sys.dbms_stats.get_prefs(preference_name) as preference_value,

global_only

from preflist;

#########################

Pdb Parameters related to AutoTask

#########################

AUTOTASK_MAX_ACTIVE_PDBS

ENABLE_AUTOMATIC_MAINTENANCE_PDB

#########################

Old Auto Task Window for daily maintenance window :

#########################

select window_name, repeat_interval, duration from dba_scheduler_windows order by window_name;

select * from dba_scheduler_window_groups;

select * from dba_scheduler_wingroup_members order by 1,2;

select client_name, status, con_id from cdb_autotask_client;

EXECUTE DBMS_SCHEDULER.SET_ATTRIBUTE('WEEKNIGHT_WINDOW','repeat_interval','freq=daily;byday=MON,TUE,WED,THU,FRI;byhour=05;byminute=0; bysecond=0');

EXECUTE DBMS_SCHEDULER.SET_ATTRIBUTE('WEEKEND_WINDOW','repeat_interval',' freq=daily;byday=SAT;byhour=07;byminute=0;bysecond=0');

EXECUTE DBMS_SCHEDULER.SET_ATTRIBUTE('MONDAY_WINDOW', 'repeat_interval','freq=daily;byday=MON;byhour=05;byminute=0; bysecond=0');

EXECUTE DBMS_SCHEDULER.SET_ATTRIBUTE('TUESDAY_WINDOW', 'repeat_interval','freq=daily;byday=TUE;byhour=05;byminute=0; bysecond=0');

EXECUTE DBMS_SCHEDULER.SET_ATTRIBUTE('WEDNESDAY_WINDOW','repeat_interval','freq=daily;byday=WED;byhour=05;byminute=0; bysecond=0');

EXECUTE DBMS_SCHEDULER.SET_ATTRIBUTE('THURSDAY_WINDOW', 'repeat_interval','freq=daily;byday=THU;byhour=05;byminute=0; bysecond=0');

EXECUTE DBMS_SCHEDULER.SET_ATTRIBUTE('FRIDAY_WINDOW', 'repeat_interval','freq=daily;byday=FRI;byhour=05;byminute=0; bysecond=0');

EXECUTE DBMS_SCHEDULER.SET_ATTRIBUTE('SATURDAY_WINDOW', 'repeat_interval','freq=daily;byday=SAT;byhour=13;byminute=0; bysecond=0');

EXECUTE DBMS_SCHEDULER.SET_ATTRIBUTE('SUNDAY_WINDOW', 'repeat_interval','freq=daily;byday=SUN;byhour=13;byminute=0; bysecond=0');

BEGIN

dbms_scheduler.disable(

name => 'WINDOW_NAME');

dbms_scheduler.set_attribute(

name => 'WINDOW_NAME',

attribute => 'DURATION',

value => numtodsinterval(6, 'hour'));

dbms_scheduler.enable(

name => 'WINDOW_NAME');

END;

BEGIN

DBMS_SCHEDULER.disable(

name => 'SYS.MAINTENANCE_WINDOW_GROUP',

force => TRUE);

DBMS_SCHEDULER.enable(

name => 'SYS.MAINTENANCE_WINDOW_GROUP');

END;

BEGIN

dbms_scheduler.create_window(

window_name=>'MORNING_WINDOW',

resource_plan=>'DEFAULT_MAINTENANCE_PLAN',

repeat_interval=>'freq=daily;byhour=10;byminute=0;bysecond=0',

duration=>interval '2' hour,

comments=>'Maintenance window');

dbms_scheduler.add_window_group_member('MAINTENANCE_WINDOW_GROUP',

'MORNING_WINDOW');

END;

BEGIN

dbms_scheduler.remove_window_group_member('MAINTENANCE_WINDOW_GROUP',

'MONDAY_WINDOW');

END;

#########################

Data Dictionary Views:

#########################

DBA_AUTOTASK_CLIENT_JOB

DBA_AUTOTASK_CLIENT

DBA_AUTOTASK_JOB_HISTORY

DBA_AUTOTASK_WINDOW_CLIENTS

DBA_AUTOTASK_CLIENT_HISTORY

DBA_AUTOTASK_OPERATION

dba_autotask_schedule

#########################

Reference :

#########################

https://tinky2jed.wordpress.com/technical-stuff/oracle-stuff/changing-the-oracle-database-default-maintenance-window-time/

https://docs.oracle.com/database/121/ADMIN/tasks.htm

Tuesday, August 27, 2024

Oracle Sql Loader handy commands

Data can be modified as it loads into the Oracle Database. One can also populate columns with static or derived values. However, this only applies for the conventional load path (and not for direct path loads

SQL*Loader provides the following methods to load data:

Conventional path loads – construct INSERT statements from the contents of the input datafile based on the predefined specification and execute the inserts.

Direct path loads – creates data blocks in Oracle database block format from the datafile and directly writes the data block to the database. This way is much faster than the conventional path but subject to some restrictions.

External table loads – create an external table for the data stored in the datafile and execute INSERT statements to insert the data from the datafile into the target table. The external table loads support parallel loading if datafile is big enough.

To execute the SQL*Load tool, you need at least three files:

The input data file stores delimited or raw data

The parameter file stores the location of the input/output files

The control file contains the specification on how data is loaded.

Sample Sql lOADER Commadns :

sqlldr username/password contorl=controlfile.ctl bad=bad.log data=data.dat logfile=log1.log direct=true parallel=true multithreading=true discard=discard.log silent=feedback

errors=1000000 bindsize=1000000 readsize=1000000 rows=1000000 multithreading=true

SQL*Loader Tuning options :

1) Direct mode

2) bindsize=1000000 readsize=1000000 rows=1000000

3) Multiple controlfile using load and skip

4) use append hint

5) multithread and parallel

Sample Control file contents :

options (errors=10000)

load data

APPEND INTO TABLE AAA ( COLUMN )

INSERT INTO TABLE SSS ( DDDD )

cat example1.ctl

load data

infile '/home/ramesh/employee.txt'

into table employee

fields terminated by ","

( id, name, dept, salary )

If you like to insert more data to the tables without having to delete the existing rows, use the “append’ command as shown in the following control file.

$ vi sqlldr-append-more.ctl

load data

infile '/home/ramesh/newemployee.txt'

append

into table employee

fields terminated by ","

( id, name, dept, salary )

LOAD DATA

INFILE *

INTO TABLE tab1 WHEN tab = 'tab1'

( tab FILLER CHAR(4),

col1 INTEGER

)

INTO TABLE tab2 WHEN tab = 'tab2'

( tab FILLER POSITION(1:4),

col1 INTEGER

)

BEGINDATA

tab1|1

tab1|2

tab2|2

tab3|3

LOAD DATA

CHARACTERSET WE8EBCDIC500

INFILE data.ebc "fix 86 buffers 1024"

BADFILE data.bad'

DISCARDFILE data.dsc'

REPLACE

INTO TABLE temp_data

(

field1 POSITION (1:4) INTEGER EXTERNAL,

field2 POSITION (5:6) INTEGER EXTERNAL,

field3 POSITION (7:12) INTEGER EXTERNAL,

field4 POSITION (13:42) CHAR,

field5 POSITION (43:72) CHAR,

field6 POSITION (73:73) INTEGER EXTERNAL,

field7 POSITION (74:74) INTEGER EXTERNAL,

field8 POSITION (75:75) INTEGER EXTERNAL,

field9 POSITION (76:86) INTEGER EXTERNAL

)

Unload data from database Table To Flat File :

set echo off newpage 0 space 0 pagesize 0 feed off head off trimspool on

spool oradata.txt

select col1 || ',' || col2 || ',' || col3

from tab1

where col2 = 'XYZ';

spool off

set colsep ','

set echo off newpage 0 space 0 pagesize 0 feed off head off trimspool on

spool oradata.txt

select col1, col2, col3

from tab1

where col2 = 'XYZ';

spool off

declare fp utl_file.file_type;

begin

fp := utl_file.fopen('c:\oradata','tab1.txt','w');

utl_file.putf(fp, '%s, %sn', 'TextField', 55);

utl_file.fclose(fp);

end;

Reference :

https://docs.oracle.com/en/database/oracle/oracle-database/19/sutil/oracle-sql-loader-commands.html#GUID-CD662CD8-DAA7-4A30-BC84-546E4C40DB31

Tuesday, July 16, 2024

Oracle options to check fragmentation and perform Table and Index reorganization

There were many request coming in for Reorg Hence thought of documenting handy article to check fragmentation and perform reorg .

After performing Reorganization we need to also gather fresh statistics . Check invalid objects pre and post Reorganization .

Article will have 2 main topics mainly

1) Ways to check Fragmentation

2) Performing Reorganization .

For Lob i have documented in my previous Blog below

https://abdul-hafeez-kalsekar.blogspot.com/2024/01/oracle-database-lob-maintenance.html

Ways to check Fragmentations :

==> High water mark(HWM) check query :

set verify off

column owner format a10

column alcblks heading 'Allocated|Blocks' just c

column usdblks heading 'Used|Blocks' just c

column hgwtr heading 'High|Water' just c

break on owner skip page

select a.owner,a.table_name,b.blocks alcblks,a.blocks usdblks,(b.blocks-a.empty_blocks-1)

hgwtr from dba_tables a,dba_segments b where a.table_name=b.segment_name

and a.owner=b.owner and a.owner not in('SYS','SYSTEM') and a.blocks <> (b.blocks-a.empty_blocks-1)

and a.owner like upper('&owner')||'%'and a.table_name like upper('&table_name')||'%'

order by 1,2;

Enter value for owner: ABDUL

Enter value for table_name: TABLE1

==> Check Fragmented Table

col TABLE_NAME for a30

col fragmented_size for a15

col table_size for a15

col Used_size for a15

select table_name,round(((blocks*8)/1024/1024),2)||'GB' "table_size",round((num_rows*avg_row_len/1024/1024/1024),2)||'GB' "Used_size",

(round(((blocks*8/1024/1024)),2)-round((num_rows*avg_row_len/1024/1024/1024),2))|| 'GB' "fragmented_size" from dba_tables

where owner not in ('SYS','SYSTEM','PERFSTAT') and last_analyzed is not null and num_rows>0 and table_name='SECURE' and owner='HAFEEZ'

and blocks >0

order by 4 asc

==> Checking Partition table fragmentation :

SELECT table_name,

partition_name,

ROUND ( (blocks / 1024 * 16), 2) "size (mb)",

ROUND ( (num_rows * avg_row_len / 1024 / 1024), 2) "actual_data (mb)",

( ROUND ( (blocks / 1024 * 16), 2)

- ROUND ( (num_rows * avg_row_len / 1024 / 1024), 2))

"wasted_space (mb)"

FROM dba_tab_partitions

WHERE (ROUND ( (blocks / 1024 * 16), 2) >

ROUND ( (num_rows * avg_row_len / 1024 / 1024), 2))

AND table_name = 'TBK_XXX'

ORDER BY 5 DESC;

select

table_owner

,table_name

,partition_name

,high_value

,compression

,compress_for

,avg_row_len

,round(((blocks*16/1024)),2)/1024 "TOTAL_SIZE_GB" --The amount of space used by the partition in gigabytes.

,round((num_rows*avg_row_len/1024/1024),2)/1024 "ACTUAL_SIZE_GB" -- The amount of space used by the partition in gigabytes, calculated based on the number of rows and the average row length.

,round(((blocks*16/1024)-(num_rows*avg_row_len/1024/1024)),2)/1024 "FRAGMENTED_SPACE_GB" --The amount of space that is not used by the partition, in gigabytes.

,decode(round(((blocks*16/1024)),2),0,0, (round(((blocks*16/1024)-(num_rows*avg_row_len/1024/1024)),2)/round(((blocks*16/1024)),2))*100) "percentage" --The percentage of unused space in the partition, calculated by dividing the unused space by the total space and multiplying by 100.

from dba_tab_partitions

WHERE

1=1

and table_owner='DEV_DW'

and table_name='TEST_TABLE'

and partition_name='SYS_P21822227'

and round(((blocks*16/1024)-(num_rows*avg_row_len/1024/1024)),2)/1024 > 0

order by 6 desc

;

==> Checking Top Fragmented Tables

select t1.owner,t1.table_name,nvl(t1.blocks*8,1) "size fragmented KB",round(nvl((t1.num_rows*t1.avg_row_len/1024),1),2) "actaul size KB",round(nvl(t1.blocks*8,1) - nvl((t1.num_rows*t1.avg_row_len/1024),1),2) "fragmentation KB"

from dba_tables t1

order by t1.owner,round(nvl(t1.blocks*8,1) - nvl((t1.num_rows*t1.avg_row_len/1024),1),2) desc ;

select blocks,last_analyzed,owner,table_name,round((blocks*8),2) "size (kb)" ,

round((num_rows*avg_row_len/1024),2) "actual_data (kb)",

(round((blocks*8),2) - round((num_rows*avg_row_len/1024),2)) "wasted_space (kb)"

from dba_tables

where (round((blocks*8),2) > round((num_rows*avg_row_len/1024),2))

and owner in ('HAFEEZ')

order by 4 ;

==> Checking Index fragmentation :

You can run the ANALYZE INDEX <index> VALIDATE STRUCTURE command on the affected indexes - each invocation of this command creates a single row in the INDEX_STATS view. This row is overwritten by the next ANALYZE INDEX command, so copy the contents of the view into a local table after each ANALYZE. The 'badness' of the index can then be judged by the ratio of 'DEL_LF_ROWS' to 'LF_ROWS'.

you may decide that index should be rebuilt if more than 20% of its rows are deleted:

ANALYZE INDEX &&index_name VALIDATE STRUCTURE;

col name heading 'Index Name' format a30

col del_lf_rows heading 'Deleted|Leaf Rows' format 99999999

col lf_rows_used heading 'Used|Leaf Rows' format 99999999

col ibadness heading '% Deleted|Leaf Rows' format 999.99999

SELECT name,

del_lf_rows,

lf_rows - del_lf_rows lf_rows_used,

to_char(del_lf_rows / (lf_rows)*100,'999.99999') ibadness

FROM index_stats

where name = upper('&index_name');

undefine index_name

select del_lf_rows * 100 / decode(lf_rows,0,1,lf_rows) from index_stats

where name = 'index_ name';

==> Checking Fragmentation using segment space advisor

set echo off

set feedback off

set verify off

set linesize 80

set serveroutput on size unlimited

spool /home/oracle/scripts/segment_advisor.txt

declare

v_task_name varchar2(100);

v_task_desc varchar2(500);

v_objid number;

begin

v_task_name := 'SEGMENT_ADVISOR_RUN';

v_task_desc := 'MANUAL SEGMENT ADVISOR RUN';

-- Create Segment Advisor task.

dbms_advisor.create_task

(

advisor_name => 'Segment Advisor',

task_name => v_task_name,

task_desc => v_task_desc

);

-- Add all segments to the task.

for s in (select segment_name, segment_type

from DBA_segments

where segment_type in ('TABLE', 'INDEX', 'LOB')

and owner != 'SYS' and owner != 'SYSTEM' and owner != 'OLAPSYS' and owner != 'SYSMAN' and owner != 'ODM' and owner != 'RMAN' and owner != 'ORACLE_OCM' and owner != 'EXFSYS' and owner != 'OUTLN' and owner != 'DBSNMP' and owner != 'OPS' and owner != 'DIP' and owner != 'ORDSYS' and owner != 'WMSYS' and owner != 'XDB' and owner != 'CTXSYS' and owner != 'DMSYS' and owner != 'SCOTT' and owner != 'TSMSYS' and owner != 'MDSYS' and owner != 'WKSYS' and owner != 'ORDDATA' and owner != 'OWBSYS' and owner != 'ORDPLUGINS' and owner != 'SI_INFORMTN_SCHEMA' and owner != 'PUBLIC' and owner != 'OWBSYS_AUDIT' and owner != 'APPQOSSYS' and owner != 'APEX_030200' and owner != 'FLOWS_030000' and owner != 'WK_TEST' and owner != 'SWBAPPS' and owner != 'WEBDB' and owner != 'OAS_PUBLIC' and owner != 'FLOWS_FILES' and owner != 'QMS')

loop

dbms_advisor.create_object

(

task_name => v_task_name,

object_type => s.segment_type,

attr1 => user,

attr2 => s.segment_name,

attr3 => null,

attr4 => null,

attr5 => null,

object_id => v_objid

);

end loop;

-- Set task parameter to recommend all.

dbms_advisor.set_task_parameter

(

task_name => v_task_name,

parameter => 'RECOMMEND_ALL',

value => 'TRUE'

);

-- Run Segment Advisor.

dbms_advisor.execute_task(v_task_name);

exception when others then

dbms_output.put_line('Exception: ' || SQLERRM);

end;

-- Output findings.

dbms_output.put_line(chr(10));

dbms_output.put_line('Segment Advisor Recommendations');

dbms_output.put_line('--------------------------------------------------------------------------------');

for r in (select segment_owner, segment_name, segment_type, partition_name,

tablespace_name, allocated_space, used_space,

reclaimable_space, chain_rowexcess, recommendations, c1, c2, c3

from table(dbms_space.asa_recommendations('TRUE', 'TRUE', 'FALSE'))

where segment_owner != 'SYS' and segment_owner != 'SYSTEM' and segment_owner != 'OLAPSYS' and segment_owner != 'SYSMAN' and segment_owner != 'ODM' and segment_owner != 'RMAN' and segment_owner != 'ORACLE_OCM' and segment_owner != 'EXFSYS' and segment_owner != 'OUTLN' and segment_owner != 'DBSNMP' and segment_owner != 'OPS' and segment_owner != 'DIP' and segment_owner != 'ORDSYS' and segment_owner != 'WMSYS' and segment_owner != 'XDB' and segment_owner != 'CTXSYS' and segment_owner != 'DMSYS' and segment_owner != 'SCOTT' and segment_owner != 'TSMSYS' and segment_owner != 'MDSYS' and segment_owner != 'WKSYS' and segment_owner != 'ORDDATA' and segment_owner != 'OWBSYS' and segment_owner != 'ORDPLUGINS' and segment_owner != 'SI_INFORMTN_SCHEMA' and segment_owner != 'PUBLIC' and segment_owner != 'OWBSYS_AUDIT' and segment_owner != 'APPQOSSYS' and segment_owner != 'APEX_030200' and segment_owner != 'FLOWS_030000' and segment_owner != 'WK_TEST' and segment_owner != 'SWBAPPS' and segment_owner != 'WEBDB' and segment_owner != 'OAS_PUBLIC' and segment_owner != 'FLOWS_FILES' and segment_owner != 'QMS'

order by reclaimable_space desc)

loop

dbms_output.put_line('');

dbms_output.put_line('Owner : ' || r.segment_owner);

dbms_output.put_line('Segment : ' || r.segment_name);

dbms_output.put_line('Segment Type : ' || r.segment_type);

dbms_output.put_line('Partition Name : ' || r.partition_name);

dbms_output.put_line('Tablespace : ' || r.tablespace_name);

dbms_output.put_line('Allocated Space : ' || r.allocated_space);

dbms_output.put_line('Used Space : ' || r.used_space);

dbms_output.put_line('Reclaimable Space in MB : ' || r.reclaimable_space/1024/1024);

dbms_output.put_line('Chain Rowexcess : ' || r.chain_rowexcess);

dbms_output.put_line('Recommendations : ' || r.recommendations);

dbms_output.put_line('Run First : ' || r.c3);

dbms_output.put_line('Run Second : ' || r.c2);

dbms_output.put_line('Run Third : ' || r.c1);

dbms_output.put_line('--------------------------------------------------------------------------------');

end loop;

-- Remove Segment Advisor task.

dbms_advisor.delete_task(v_task_name);

end;

spool off;

Ways to remove Fragmentations :

Main ways commonly followed are :

Shrink

Alter table Move

CTAS method

Datapump or exp/imp

==> Options to Perform Reorg of Table

SQL> ALTER TABLE table name ENABLE ROW MOVEMENT;

SQL> ALTER TABLE table name SHRINK SPACE CASCADE;

SQL> ALTER TABLE table name DISABLE ROW MOVEMENT;

ALTER TABLE mytable MOVE PARALLEL (DEGREE 8) ONLINE UPDATE INDEXES

==> Options to Perform Reorg of Partition Table

ALTER TABLE TEST_TABLE enable row movement;

ALTER TABLE order MODIFY PARTITION SYS_P21674395 SHRINK SPACE;

ALTER TABLE order MOVE PARTITION SYS_P21674395 UPDATE INDEXES;

ALTER TABLE order MOVE PARTITION SYS_P21674395 ONLINE UPDATE INDEXES;

ALTER TABLE TEST_TABLE move PARTITION SYS_P21822227 NOCOMPRESS UPDATE INDEXES;

ALTER TABLE order MOVE PARTITION SYS_P21674395 COMPRESS FOR QUERY HIGH UPDATE INDEXES;

==> Options to Perform rebuild of index / Remove Index Fragmentation

ALTER TABLE four_seasons MODIFY PARTITION quarter_two REBUILD UNUSABLE LOCAL INDEXES;

ALTER INDEX sales_area_ix REBUILD PARTITION jan99_ix;

ALTER INDEX index name SHRINK SPACE;

ALTER INDEX SCOTT.EMP_IDX REBUILD ONLINE parallel 10 ;

Check the progress of Alter Shrink Space Command

-- Following command will search alter table command and give you output how much it covered according to table size in first command.

-- GB_read give you how much it covered yet.

select a.event, a.WAIT_TIME, c.SQL_TEXT,

c.PHYSICAL_READ_BYTES / 1024 / 1024 / 1024 "GB_READ",

c.PHYSICAL_WRITE_BYTES / 1024 / 1024 / 1024 "GB_WRITE"

from v$session_wait a , v$session b , v$sql c

where UPPER(c.SQL_TEXT) like UPPER('%ALTER TABLE%')

and a.sid = b.sid

and b.SQL_ID = c.SQL_ID;

--If you have session id of session from which command running then use following command:

select a.event, a.WAIT_TIME, c.SQL_TEXT,

c.PHYSICAL_READ_BYTES / 1024 / 1024 / 1024 "GB_READ",

c.PHYSICAL_WRITE_BYTES / 1024 / 1024 / 1024 "GB_WRITE"

from v$session_wait a , v$session b , v$sql c

where a.SID =

and a.sid = b.sid

and b.SQL_ID = c.SQL_ID;

Online Redefinition to perform Reorg :

A primary key is mandatory since materialized views and logs are created during the start of redefinition.

The user performing the re-organization requires the following

privileges:

* CREATE ANY TABLE

* ALTER ANY TABLE

* DROP ANY TABLE

* LOCK ANY TABLE

* SELECT ANY TABLE

* CREATE ANY INDEX

* CREATE ANY TRIGGER

GENERAL STEPS TO ONLINE REDEFINE A TABLE

1) Determine if the table to be moved can be redefined online (DBMS_REDEFINITION.CAN_REDEF_TABLE)

2) Create the interim table

The interim table need not be the same 'shape' (have similar structure) as the original table

3) Start the redefinition of the table (DBMS_REDEFINITION.START_REDEF_TABLE)

4) Copy the dependents from the original table to the interim table (DBMS_REDEFINITION.COPY_TABLE_DEPENDENTS)

5) Execute a final synchronization between the original and interim tables (DBMS_REDEFINITION.SYNC_INTERIM_TABLE)

This step will minimize the amount of time needed to execute the finish of the redefinition

6) Finish the redefinition (DBMS_REDEFINITION.FINISH_REDEF_TABLE)

7) Verify that the redefinition succeeded by comparing the original table (formerly interim) to the interim table (formerly original)

8) Drop the interim table

---------------------------------------------------------------------

-- Test if table can be redefined...

---------------------------------------------------------------------

SET SERVEROUTPUT ON

begin

DBMS_REDEFINITION.CAN_REDEF_TABLE

(

uname=>'SCOTT',

tname=>'emp' );

end;

---------------------------------------------------------------------

-- CREATE THE INTERIM TABLE

---------------------------------------------------------------------

create table emp_work (

COL1 NUMBER,

COL2 VARCHAR2(1000),

COL3 VARCHAR2(1000),

COL4 VARCHAR2(1000));

---------------------------------------------------------------------

-- Start table redefinition...

---------------------------------------------------------------------

During this phase Oracle will copy (and transform) the data from the production table to the interim table. Oracle will also create a materialized view (snapshot) log on the table to track DML changes.

SET SERVEROUTPUT ON

begin

DBMS_REDEFINITION.start_redef_table(

uname=>'SCOTT',

orig_table=>'emp',

int_table=>'emp_work');

end;

---------------------------------------------------------------------

-- COPY THE TABLE DEPENDENTS FROM THE ORIGINAL TABLE TO THE INTERIM TABLE

---------------------------------------------------------------------

SET SERVEROUTPUT ON

DECLARE

l_num_errors PLS_INTEGER;

begin

DBMS_REDEFINITION.COPY_TABLE_DEPENDENTS(

uname=>'SCOTT',

orig_table=>'emp',

int_table=>'emp_work',

copy_indexes => DBMS_REDEFINITION.cons_orig_params,

copy_triggers => TRUE,

copy_constraints => TRUE,

copy_privileges => TRUE,

ignore_errors => FALSE,

num_errors => l_num_errors);

end;

--------------------------------------------------------------------

-- Do necessary changes: here we Create constraints on the interim table ( skip thisif only reorganization is needec )

---------------------------------------------------------------------

SQL> alter table emp_work add constraint int_empx_pk primary key(empno);

SQL> alter table emp_work add constraint 2 int_empx_fk foreign key(deptno) references dept(deptno);

SQL> alter table emp_work MODIFY CONSTRAINT int_empx_fk 2 DISABLE KEEP INDEX;

---------------------------------------------------------------------

-- Sync intermediate changes to interim table (optional)

---------------------------------------------------------------------

This step will apply changes captured in the materialized view log to the interim table. Perform this step frequently for high transaction tables.

SQL> exec dbms_redefinition.sync_interim_table('scott', 'emp', 'emp_work');

---------------------------------------------------------------------

-- Finish the redefinition process (this will swap the two tables)...

---------------------------------------------------------------------

EXEC DBMS_REDEFINITION.FINISH_REDEF_TABLE('scott', 'emp', 'emp_work');

---------------------------------------------------------------------

-- Drop the interim working table...

---------------------------------------------------------------------

DROP TABLE emp_work;

Redefine table without primary Key :

The Reason the table failed is because the Online redefinition happens either by using a primary key or using ROWID,

The Default is the Primary Key,

If we dont haveprimary key we need to use rowid option . For that "options_flag=>DBMS_REDEFINITION.cons_use_rowid" needs to be added in DBMS_REDEFINITION.CAN_REDEF_TABLE and DBMS_REDEFINITION.start_redef_table function

SET SERVEROUTPUT ON

begin

DBMS_REDEFINITION.CAN_REDEF_TABLE(

uname=>'SCOTT',

tname=>'emp',

options_flag=>DBMS_REDEFINITION.cons_use_rowid);

end;

SET SERVEROUTPUT ON

begin

DBMS_REDEFINITION.start_redef_table(

uname=>'SCOTT',

orig_table=>'emp',

int_table=>'emp_work',

options_flag=>DBMS_REDEFINITION.cons_use_rowid);

end;

-- To perform online redefinition in parallel

alter session force parallel dml parallel 32;

alter session force parallel query parallel 32;

References :

https://oracle-base.com/articles/12c/online-move-partitions-and-subpartitions-12cr1#google_vignette

https://docs.oracle.com/en/database/oracle/oracle-database/12.2/vldbg/maintenance-partition-tables-indexes.html#GUID-CDAA2363-B83A-408C-82C9-3E3FA3928D2D

https://docs.oracle.com/en/database/oracle/oracle-database/18/vldbg/maintenance-partition-tables-indexes.html#GUID-BAFFE31C-07A2-4ED6-BDCF-8ECB79D7FE7D

Attempt to reduce the size of a LOB segment after the table / LOB becomes sparse -> How to Shrink (make less sparse) a LOB (BASICFILE or SECUREFILE)? (Doc ID 1451124.1)

How to Re-Organize a Table Online (Doc ID 177407.1)

How to release unused space (SHRINK) occupied by a LOB segment by adding / dropping columns? (Doc ID 1417697.1)

How to Shrink (make less sparse) a LOB (BASICFILE or SECUREFILE)? (Doc ID 1451124.1)

Sunday, June 16, 2024

Restore Table Into dumpfile using Oracle database Rman Backup of Pluggable database

There are many documents Online for this but since we had requirement to perform same thought of documenting my own

Instead of importing table in same database its preferable to import into dump file .

Below is the high level procedure on how the restoration works.

1) Identifies the set of tablespace that needs to be recovered for this table restore.

2) Creates temporary instance with a random unique name

3) Starts database in nomount state and performs control file restore based on until time/scn value defined.

4) Sets new destinations for the identified data files to be restored

5) Then initiates the restoration of SYSTEM,SYSAUX,UNDO tablespaces for CDB and SYSTEM and SYSAUX and EXAMPLE tablespace for PDB

6) Perform recovery of database until time/scn by restoring archive logs and applying them to temporary database.

7) Once done its open the Database in open read only along with any PDB database under which table is available

8) Restart in nomount state and initiate restoraton of Datafiles related to Application Table(User Tablespace datafiles)

9) Recover archive logs and apply until time/scn

10) RMAN opens database and creates temporary DBA Directory to hold expdp dump

11) Performs expdp dump of table

12) Shutdown abort temporary database

13) Import the table dump to Source database

14) Cleanup all files created at the end of session

1) Restore table into dumpfile

Create a pfile for auxiliary db use /tmp/init_aux.ora . Username and Table name must be in caps

Add below parameter in it (Ensure other parameters like db_name/sga are specified along with it)

_disable_health_check=true

Main parameters to be added to auxiliary pfile are

enable_pluggable_database=true

_clone_one_pdb_recovery=true

wallet_root

tde_configuration

compatible

db_block_size

db_files

diagnostic_dest

_system_trigger_enabled =false

db_domain

sga_target

db_create_files_dest ( to auxiliary destination used in restore )

log_archive_dest_1 ( to auxiliary destination used in restore )

db_name

db_unique_name

rman target=/

RUN {

SET AUXILIARY INSTANCE PARAMETER FILE TO '/tmp/init_aux.ora';

recover table "MYUSER"."MYTABLE" OF PLUGGABLE DATABASE pdb2

until scn 37128783

auxiliary destination '/tmp/aux'

datapump destination '/var/oracle/data/export'

dump file 'saved_copy.dmp'

notableimport;

}

RUN {

SET AUXILIARY INSTANCE PARAMETER FILE TO '/tmp/init_aux.ora';

recover table "MYUSER"."MYTABLE" OF PLUGGABLE DATABASE nameofpluggabledb

until time "to_date('07/11/2022 16:34:10','dd/mm/yyyy hh24:mi:ss')"

auxiliary destination '/var/oracle/backup/aux'

datapump destination '/var/oracle/backup/datapump'

dump file 'saved_copy.dmp'

notableimport;

}

If we want to import directly in database we can use below

RUN {

SET AUXILIARY INSTANCE PARAMETER FILE TO '/tmp/init_aux.ora';

recover table "MYUSER"."MYTABLE" OF PLUGGABLE DATABASE nameofpluggabledb

until time "to_date('07/11/2022 16:34:10','dd/mm/yyyy hh24:mi:ss')"

auxiliary destination '/var/oracle/backup/aux'

REMAP TABLE 'SMEDS'.'RECTEST':'TEST_RECTEST';

}

2) Import dumpfile in database from above dmpfile

impdp youruser/yourpassword@yourhost/nameofpluggabledb full=Y directory=DUMP_DIR dumpfile=saved_copy.dmp

References :

Rman Recover Table Doesnot Clean up Files Created Under Dbs Folder For the Auxiliary Instance After it Completes (Doc ID 2882639.1)

RMAN Recover Table Feature in Oracle Database 12c and Higher (Doc ID 1521524.1)

Undo Datafile at Auxiliary Instance Remains after Executing Recover Table (Doc ID 2407419.1)

Monday, May 20, 2024

Oracle Handling Distributed, Pending , In-Doubt and Remote Transaction

A distributed transaction modifies data related to two or more databases, it contains DML statements than span many nodes. For a distributed transaction to be succesful all or none of the database nodes involved in the transaction need to commit or rollback the whole transaction.

Note the difference between a distributed and a remote transaction; a remote transaction contains one or more DML statements that are executed on the SAME remote node,

Manual Resolution of In-Doubt Transactions

–The in-doubt transaction has locks on critical data or undo segments.

–The cause of the system, network, or software failure cannot be repaired quickly.

Commit or Rollback Pending Transaction -- UNSTUCK TRANSACTION :

SQL> select local_tran_id,global_tran_id, state,mixed, commit# from dba_2pc_pending;

If the state of the transaction is “prepared” and there is no inconsistency, the transaction can be forced to rollback, or maybe if the underlying problem which caused the in-doubt transaction is resolved the transaction can be forced to commit as follows:

SQL> ROLLBACK FORCE '97.33.166765' /* ->replace with ur own trx_id */

SQL> COMMIT FORCE '97.33.166765' /* ->replace with ur own trx_id */

If the state of the transaction is “collecting” and you execute the above command, you may see an error like:

ERROR at line 1:

ORA-02058: no prepared transaction found with ID 97.33.166765

DBA_2PC_PENDING view have entries about our transaction but there is no transaction in reality

If the state of the transaction (in DBA_2PC_PENDING) is committed, rollback forced or commit forced then it can be cleaned by:

SQL> EXECUTE DBMS_TRANSACTION.PURGE_LOST_DB_ENTRY('97.33.166765'); /* ->replace with ur own trx_id */

HANDLING STUCK TRANSACTIONS

Our ultimate goal is not seeing the transaction in X$KTUXE table; and ensuring that the dictionary tables like PENDING_TRANS$ to be consistent with this information.

Stuck transactions can be examined under the below conditions:

2.1. Condition 1: DBA_2PC_PENDING view have entries about our transaction but there is no transaction in reality

The condition is that; when we issue select to the dictionary views like the DBA_2PC_PENDING, PENDING_TRANS$, etc. we see the transaction, but the transaction does not exist in X$KTUXE view.

The actual transaction entry view is X$KTUXE ([K]ernel [T]ransaction [U]ndo Transa[X]tion [E]ntry) where the columns correspond to the following sections of the transaction id:

KTUXEUSN.KTUXESLT.KTUXESQN = 96.22.163456 (The concat of KTUXEUSN, KTUXESLT and KTUXESQN gives us the transacion number)

KTUXEUSN=96

KTUXESLT=22

KTUXESQN=163456

Therefore, the condition1 holds when DBA_2PC_PENDING has the entry but X$KTUXE does not.

SQL> SELECT LOCAL_TRAN_ID, GLOBAL_TRAN_ID, STATE, MIXED, COMMIT# FROM DBA_2PC_PENDING;

-- Returns: 96.22.163456 TESTDB.723a8559.96.22.163456 prepared no 56759427464

SQL> SELECT * FROM X$KTUXE WHERE KTUXEUSN=96 AND KTUXESLT=22 AND KTUXESQN =163456;

-- Returns: No Rows

Solution 1 to Condition 1: If the state of the transaction (in DBA_2PC_PENDING) is committed, rollback forced or commit forced then it can be cleaned by:

SQL> EXECUTE DBMS_TRANSACTION.PURGE_LOST_DB_ENTRY('96.22.163456');

Solution 2 to Condition 1: If the state of the transaction is prepared, we have to clean manually as follows:

SQL> DELETE FROM SYS.PENDING_TRANS$ WHERE LOCAL_TRAN_ID = '96.22.163456';

SQL> DELETE FROM SYS.PENDING_SESSIONS$ WHERE LOCAL_TRAN_ID ='96.22.163456' ;

SQL> DELETE FROM SYS.PENDING_SUB_SESSIONS$ WHERE LOCAL_TRAN_ID = '96.22.163456';

SQL> COMMIT;

2.2. Condition 2: DBA_2PC_PENDING view does NOT have entries about our transaction but there IS A transaction.

This is something like a orphan transaction that the dictionary is not aware of.

Trying to force commit or rollback this transaction may result in error like below, since the dictionary is not aware:

SQL> ROLLBACK FORCE '96.22.163456'

-- ORA-02058: no prepared transaction found with ID 96.22.163456

Solution to Condition 2: What we need to do at this point is; recovering our transaction from being an orphan by inserting some dummy records into dictionay tables (so the views…) and then force a rollback or commit: You do not have to change the parameters in the insert command other than the transaction id.

SQL> ALTER SYSTEM DISABLE DISTRIBUTED RECOVERY;

SQL> INSERT INTO PENDING_TRANS$ (LOCAL_TRAN_ID, GLOBAL_TRAN_FMT, GLOBAL_ORACLE_ID, STATE, STATUS, SESSION_VECTOR, RECO_VECTOR, TYPE#, FAIL_TIME,RECO_TIME)

VALUES

(

'96.22.163456',

299354,

'XXXXXXX.12345.1.2.3',

'prepared','P',

hextoraw( '00000001' ),

hextoraw( '00000000' ),

0, sysdate, sysdate

);

SQL> INSERT INTO PENDING_SESSIONS$

VALUES

(

'96.22.163456',

1, hextoraw('05004F003A1500000104'),

'C', 0, 30258592, '',

146

);

SQL> COMMIT;

Now, we should be able to rollback or commit.

SQL> ROLLBACK FORCE '96.22.163456'

SQL> COMMIT FORCE '96.22.163456'

Lastly, we remove the dummy entry from the dictionary:

SQL> ALTER SYSTEM ENABLE DISTRIBUTED RECOVERY;

SQL> ALTER SYSTEM SET "_smu_debug_mode" = 4;

SQL> COMMIT;

SQL> EXECUTE DBMS_TRANSACTION.PURGE_LOST_DB_ENTRY('96.22.163456');

SQL> ALTER SYSTEM SET "_smu_debug_mode" = 0;

SQL> COMMIT;

Check to see whether the transaction has gone:

SQL> SELECT * FROM X$KTUXE WHERE KTUXEUSN=96 AND KTUXESLT=22 AND KTUXESQN =163456;

-- Returns: No Rows

2.3. Condition 3: DBA_2PC_PENDING has entry and there is a transaction but COMMIT or ROLLBACK HANGS!

In the situation, where COMMIT FORCE or ROLLBACK FORCE hangs,

Trying to purge the transaction will give an error like:

SQL> EXECUTE DBMS_TRANSACTION.PURGE_LOST_DB_ENTRY('96.22.163456');

-- ERROR at line 1:

-- ORA-06510: PL/SQL: unhandled user-defined exception

-- ORA-06512: at "SYS.DBMS_TRANSACTION", line 94

-- ORA-06512: at line 1

Solution to Condition 3: The solution is the combination of Cond1 and Cond2:

First, delete the dictionary entries:

SQL> DELETE FROM SYS.PENDING_TRANS$ WHERE LOCAL_TRAN_ID = '96.22.163456';

SQL> DELETE FROM SYS.PENDING_SESSIONS$ WHERE LOCAL_TRAN_ID ='96.22.163456' ;

SQL> DELETE FROM SYS.PENDING_SUB_SESSIONS$ WHERE LOCAL_TRAN_ID = '96.22.163456';

SQL> COMMIT;

Then, insert dummy record, force commit and finally purge the transaction:

SQL> ALTER SYSTEM DISABLE DISTRIBUTED RECOVERY;

SQL> INSERT INTO PENDING_TRANS$ (LOCAL_TRAN_ID, GLOBAL_TRAN_FMT, GLOBAL_ORACLE_ID,

STATE, STATUS, SESSION_VECTOR, RECO_VECTOR, TYPE#, FAIL_TIME,RECO_TIME)

VALUES

(

'96.22.163456',

306206,

'XXXXXXX.12345.1.2.3',

'prepared','P',

hextoraw( '00000001' ),

hextoraw( '00000000' ),

0, sysdate, sysdate

);

SQL> INSERT INTO PENDING_SESSIONS$

VALUES

(

'96.22.163456',

1, hextoraw('05004F003A1500000104'),

'C', 0, 30258592, '',

146

);

SQL> COMMIT;

SQL> COMMIT FORCE '96.22.163456';

SQL> EXECUTE DBMS_TRANSACTION.PURGE_LOST_DB_ENTRY('96.22.163456');

Two-Phase Commit (2PC)

The two phase-commit mechanism is used to ensure data integrity in a distributed transaction. It is automatically used during all distributed transactions and coordinates either the commit or roll back of all the changes in the transaction as a single, self-contained unit.

In short, there are three phases for the 2PC:

PREPARE: The initiating node ask each of its referenced nodes to promise to perform a commit or rollback when told to do so. The preparing node will flush the redo log buffer to the online redo log. It converts locks to in-doubt transaction locks on the data blocks and passes its highest SCN value to the initiating node.

COMMIT: The initiating node commits and writes to its redo log the committed SCN. The Data Block locks are released.

FORGET: Pending transactions tables are related database views are cleared (dba_2pc_pending/dba_2pc_neighbors)

All the above phases take place quickly and transparently to the application where the transaction originated.

NOTE:

A crash during the PREPARE Phase results in a ROLLBACK

A crash during the COMMIT Phase results in either COMMIT or ROLLBACK

Recoverer Process (RECO)

RECO is a mandatory background process that, in a distributed database, automatically resolves failures in distributed transactions. The RECO process of a node automatically connects to other databases involved in an in-doubt distributed transaction; it can use an existing connection or establish a new connection to other nodes involved in the failed transaction.. When RECO reestablishes a connection between the databases, it automatically resolves all in-doubt transactions, removing from each database's pending transaction table any rows that correspond to the resolved transactions.

At exponentially growing time intervals, the RECO background process of a node attempts to recover the local portion of an in-doubt distributed transaction.

init.ora parameter distributed_transactions > 0 (for RECO to start)

If init.ora open_links is set to 0, then no distributed transactions are allowed.

The RECO process is present only if the instance permits distributed transactions.

You can enable and disable RECO using the ALTER SYSTEM statement with the ENABLE/DISABLE DISTRIBUTED RECOVERY options.

You can disable distributed recovery if the database is mounted but not open.

select dbid,name,log_mode,open_mode from v$database;

select instance_number,instance_name,status from v$instance;

Disabling and Enabling RECO

You can enable and disable RECO using the ALTER SYSTEM statement with the ENABLE/DISABLE DISTRIBUTED RECOVERY options. For example, you can temporarily disable RECO to force the failure of a two-phase commit and manually resolve the in-doubt transaction.

-To disable RECO:

ALTER SYSTEM DISABLE DISTRIBUTED RECOVERY

-To enable RECO and let it automatically resolve indoubt transactions

ALTER SYSTEM ENABLE DISTRIBUTED RECOVERY;

Database Parameters related to distributed Transactions :

DISTRIBUTED_LOCK_TIMEOUT :

DISTRIBUTED_LOCK_TIMEOUT is used to specify maximum time in seconds that instance waits for locked resources . Default is 60 seconds

COMMIT_POINT_STRENGTH :

In a two phase commit process, one site or node is the designated “Commit Point Site” . This is determined by the values of the

COMMIT_POINT_STRENGTH parameter in all the database instances involved in the transaction which are adjacent to and include the Global Coordinator

The values range from 0 to 255 and if not set then the is determined by the software

The COMMIT_POINT_STRENGTH parameter in nonadjacent nodes is only used to resolve who will be the recursive“Commit Point Site” when a Local

Coordinator is the main “Commit Point Site"

Known Issues :

ORA-02053: transaction committed, some remote DBs may be in-doubt

The transaction has been locally committed, however we have lost communication with one or more local coordinators.

ORA-02054: transaction in-doubt

The transaction is neither committed or rolled back locally, and we have lost communication with the global coordinator.

ORA-02050: transaction rolled back, some remote DBs may be in-doubt

Indicates that a communication error ocurred during the two-phase commit

ORA-01591: lock held by in-doubt distributed transaction

Encountering the above error and users/applications unable to proceed with their work. In this case, Oracle automatically rolls back the user attempted transaction and the DBA has now to manually commit or rollback the in-doubt transaction.

Views :

DBA_2PC_PENDING and DBA_2PC_NEIGHBORS are 2 main views used for checking details

DBA_2PC_PENDING

view to determine the global commit number for a particular transaction ID. Lists all in-doubt distributed transactions.

The view is empty until populated by an in-doubt transaction. After the transaction is resolved, the view is purged

Note: When LOCAL_TRAN_ID and GLOBAL_TRAN_ID value is same then node is the global coordinator of the transaction.

1) LOCAL_TRAN_ID : Local transaction identifier

2) GLOBAL_TRAN_ID : Global database identifier

3) STATE : –Collecting: node is currently collecting information from other database servers before it can decide whether it can prepare.

–Prepared: Node has prepared and holding locks on resources. May or not acknowledge to local coordinator

–Committed: Node has committed the transaction but other node may or may not done.

–Forced Commit: Administrator manually forced to commit the pending transaction at local node.

–Forced rollback: A pending transaction forced to rollback at local node.

4) MIXED: YES means part of transaction committed on one node and rollback at other node.

5) TRAN_COMMENT: Transaction comment

6) HOST: Hostname

7) COMMIT# : Global commit number for committed transaction

COL LOCAL_TRAN_ID FORMAT A13

COL GLOBAL_TRAN_ID FORMAT A30

COL STATE FORMAT A8

COL MIXED FORMAT A3

COL HOST FORMAT A10

COL COMMIT# FORMAT A10

SELECT LOCAL_TRAN_ID, GLOBAL_TRAN_ID, STATE, MIXED, HOST, COMMIT# FROM DBA_2PC_PENDING;

DBA_2PC_NEIGHBORS :

Lists all incoming and outgoing in-doubt distributed transactions. It also indicates whether the local node is the commit point site in the transaction.

1) LOCAL_TRAN_ID: Local transaction identifier

2) IN_OUT: IN for incoming transactions; OUT for outgoing transactions

3) DATABASE: For incoming transactions, the name of the client database for outgoing transactions, the name of the database link used to access information on a remote server.

4) DBUSER_OWNER: For incoming transactions, the local account used to connect, for outgoing transactions: the owner of the database link.

5) INTERFACE: C is a commit message; N is either indicating a prepared state or read-only commit.

COL LOCAL_TRAN_ID FORMAT A13

COL IN_OUT FORMAT A6

COL DATABASE FORMAT A25

COL DBUSER_OWNER FORMAT A15

COL INTERFACE FORMAT A3

SELECT LOCAL_TRAN_ID, IN_OUT, DATABASE, DBUSER_OWNER, INTERFACE FROM DBA_2PC_NEIGHBORS

Other views :

SQL> SELECT * FROM GLOBAL_NAME;

SQL> select * from DBA_2PC_PENDING;

SQL> select * from DBA_2PC_NEIGHBORS;

SQL> select * from sys.pending_trans$;

SQL> select * from SYS.PENDING_SESSIONS$;

SQL> select * from SYS.PENDING_SUB_SESSIONS$;

SQL> select * from SYS.V$GLOBAL_TRANSACTION ;

SELECT

ktuxeusn usn# -- 65535 = no-undo transaction

, ktuxeslt slot# -- 65535 = invalid slot#

, ktuxesqn seq#

, ktuxesta status

, ktuxecfl flags

, ktuxesiz undo_blks

, ktuxerdbf curfile

, ktuxerdbb curblock

, ktuxescnw * power(2, 32) + ktuxescnb cscn -- commit/prepare commit SCN

, ktuxeuel

-- distributed xacts

--, ktuxeddbf r_rfile

--, ktuxeddbb r_rblock

--, ktuxepusn r_usn#

--, ktuxepslt r_slot#

--, ktuxepsqn r_seq#

FROM

x$ktuxe

WHERE ktuxesta != 'INACTIVE'

ORDER BY

ktuxeusn

, ktuxeslt

SELECT

"AREA NAME" -- VARCHAR2(32)

, "NUMAPG" -- NUMBER

, "PAGESIZE" / 1024 mempage_kb -- NUMBER

, ROUND("SEGMENT SIZE" / 1048576) segsize_mb -- NUMBER

, ROUND("SIZE" / 1048576) area_size_mb -- NUMBER

, ROUND("REMAINING ALLOC SIZE" / 1048576) remain_mb -- NUMBER

, "SHMID" -- NUMBER

, "SEGMENT DISTRIBUTED" -- VARCHAR2(20)

, "AREA FLAGS" -- NUMBER

, "SEGMENT DEFERRED" -- VARCHAR2(20)

, "SEG_START ADDR" -- RAW(8)

, "START ADDR" -- RAW(8)

FROM

x$ksmssinfo

Before Rollback or committing please capture below details as If these transaction were XA transactions, the responsibility of cleaning them up would be the external transaction manager.

***********************

SET MARKUP HTML ON SPOOL ON HEAD "<TITLE>2PC - INFO </title> -

<STYLE TYPE='TEXT/CSS'></STYLE>"

SET ECHO OFF

REM Spooling to html file

REM Insert the queries to be executed between the SPOOL commands.

define COLLNAME='SUP_'

define SRDCNAME='2PC'

column SRDCSPOOLNAME new_val SRDCSPOOLNAME

--select 'SRDC_'||upper('&&SRDCNAME')||'_'||upper(instance_name)||'_'||to_char(sysdate,'YYYYMMDD_HH24MISS')||'.htm' SRDCSPOOLNAME from v$instance;

select '&&COLLNAME'||upper('&&SRDCNAME')||'_'||upper(instance_name)||'_CDB_'||upper(cdb)||'_'||to_char(sysdate,'YYYYMMDD_HH24MISS')||'.htm' SRDCSPOOLNAME from v$instance, v$database;

spool &SRDCSPOOLNAME

ALTER SESSION set NLS_DATE_FORMAT='MM/DD/YY HH24:Mi:SS';

set pagesize 1000

select sysdate from dual;

SELECT SYS_CONTEXT ('USERENV', 'CON_NAME') "Current Container" FROM DUAL;

select con_id, name, cdb, current_scn from gv$database order by inst_id;

select * from gv$containers order by inst_id,con_id;

select * from gv$pdbs order by inst_id,con_id;

select * from gv$version;

select * from global_name;

select * from dba_2pc_pending;

select * from dba_2pc_neighbors;

select * from sys.pending_trans$;

select * from sys.pending_sessions$;

select * from sys.pending_sub_sessions$;

select * from v$session_wait order by SECONDS_IN_WAIT;

SELECT KTUXEUSN, KTUXESLT, KTUXESQN, /* Transaction ID */

KTUXESTA Status,

KTUXECFL Flags

FROM x$ktuxe

WHERE ktuxesta!='INACTIVE';

prompt +++ In memory transaction +++

select /*+ ORDERED */

'----------------------------------------'||'

Curent Time : '|| substr(to_char(sysdate,' HH24.MI.SS'),1,22) ||'

'||'TX start_time: '||t.KTCXBSTM||'

'||'FORMATID: '||g.K2GTIFMT ||'

'||'GTXID: '||g.K2GTITID_EXT ||'

'||'Branch: '||g.K2GTIBID ||'

Local_Tran_Id ='||substr(t.KXIDUSN||'.'||t.kXIDSLT||'.'||t.kXIDSQN,1,15)||'

'||'KTUXESTA='|| x.KTUXESTA ||'

'||'KTUXEDFL='|| x.KTUXECFL ||'

Lock_Info: ID1: ' || ((t.kXIDUSN*64*1024)+ t.kXIDSLT)

||' ID2: '|| t.kXIDSQN

XA_transaction_INFO

from x$k2gte g, x$ktcxb t, x$ktuxe x

where g.K2GTDXCB =t.ktcxbxba and

x.KTUXEUSN = t.KXIDUSN(+) and

x.KTUXESLT = t.kXIDSLT(+) and

x.KTUXESQN =t.kXIDSQN(+);

prompt +++ Timed out, prepared XA transactions +++

select global_tran_fmt, global_foreign_id, branch_id,state,

tran.local_tran_id

from sys.pending_trans$ tran, sys.pending_sessions$ sess

where tran.local_tran_id = sess.local_tran_id

and tran.state = 'prepared'

and dbms_utility.is_bit_set(tran.session_vector, sess.session_id)=1;

select sid, type, id1, id2, lmode, request from GV$lock

where type = 'TM' or type = 'TX';

select LOCAL_TRAN_ID, GLOBAL_TRAN_ID,to_char(FAIL_TIME,'dd-mm-yyyy HH24:MI:SS') FAIL_TIME,STATE, MIXED from DBA_2PC_PENDING;

select NAME, VALUE from V$PARAMETER where upper(NAME) = 'COMPATIBLE';

select NAME, VALUE from V$PARAMETER where upper(NAME) = 'DISTRIBUTED_LOCK_TIMEOUT';

select OWNER, OBJECT_NAME, OBJECT_TYPE, STATUS from DBA_OBJECTS where OBJECT_NAME like 'DBMS_XA%' order by OWNER, OBJECT_NAME, OBJECT_TYPE;

select blocking_session, sid, serial#,event, wait_class, seconds_in_wait

from v$session

where blocking_session is not NULL

order by blocking_session;

spool off

SET MARKUP HTML OFF

SET ECHO ON

***********************

References :

Distributed Database, Transactions and Two Phase Commit (Doc ID 13229.1)

https://dbatrain.wordpress.com/wp-content/uploads/2009/01/database-links-masterclass_2.pdf

https://docs.oracle.com/en/database/oracle/oracle-database/12.2/admin/managing-distributed-transactions.html#GUID-AB19431E-BF9F-4181-BC57-699F8A06149D

Primary Note for Troubleshooting Oracle Managed Distributed Transactions (Doc ID 100664.1)

https://www.linkedin.com/pulse/resolve-in-doubt-transactions-handling-unstuck-mohsen-taheri/

https://oraclefiles.com/2019/03/04/resolving-in-doubt-transactions/

Saturday, May 18, 2024

Storing Oracle user password in Oracle wallet on client side

We have move to Exacc , using OS authentication for application user was challenge and we have to arrange other Secure External Password Store .

Thanks to Oracle Doc 340559.1 that shared steps on using Oracle wallet on client side .

When clients are configured to use the secure external password store, applications can connect to a database with the following CONNECT statement syntax, without specifying database login credentials:

connect /@db_connect_string

where db_connect_string is a valid connect string to access the intended database. In this case, the database credentials, username and password,

are securely stored in an Oracle wallet created for this purpose. The autologin feature of this wallet is turned on so the system does not need a password to open the wallet.

From the wallet, it gets the credentials to access the database for the user they represent.

Configuring Clients to Use the External Password Store

1) Create a wallet on the client by using the following syntax at the command line:

$ORACLE_HOME/oracle_common/bin/mkstore -wrl <wallet_location> -create ( need to input wallet password once asked )

2) Create database connection credentials in the wallet by using the following syntax at the command line:

mkstore -wrl <wallet_location> -createCredential <db_connect_string> <username> <password>

example:

("N102" in the following example is a connect descriptor located in the tnsnames.ora.)

mkstore -wrl /home/mseibt/pstore -createCredential N102 <user> <password>

Enter password: welcome1

3) In the client sqlnet.ora file, enter the WALLET_LOCATION parameter and set it to the directory location of the wallet you created in Step 1.

WALLET_LOCATION =

(SOURCE =

(METHOD = FILE)

(METHOD_DATA = (DIRECTORY = /home/mseibt/pstore))

)

SQLNET.WALLET_OVERRIDE = TRUE

SSL_CLIENT_AUTHENTICATION = FALSE

SSL_VERSION = 0

4) In the client sqlnet.ora file, enter the SQLNET.WALLET_OVERRIDE parameter and set it to TRUE

SQLNET.WALLET_OVERRIDE = TRUE

5) With the external password store configured, connect as <user>:

sqlplus /@N102

--Datapump using wallet

nohup expdp /@BSA1EP directory=DUMP_DIR dumpfile=scott_%U.dmp logfile=EXP_SCOTT.log schemas=scott parallel=4 &

-- JDBC using wallet

Connection conn = DriverManager.getConnection ("jdbc:oracle:oci:/@BSA1EP");

-- sqlplus

sqlplus /@BSA1EP

Managing External Password Store Credentials

1) Listing the contents of the external password store:

mkstore -wrl /home/mseibt/pstore -listCredential

2) Adding database login credentials to an existing client wallet:

mkstore -wrl /home/mseibt/pstore -createCredential N101 <user><password>

3) Modifying database login credentials in a wallet:

mkstore -wrl /home/mseibt/pstore -modifyCredential N102 <user> newpassword

4) Deleting database login credentials from a wallet:

mkstore -wrl /home/mseibt/pstore -deleteCredential N101

5) Listing wallet entries:

mkstore -wrl /home/mseibt/pstore -list

6) Listing entry values:

The name will be something like oracle.wallet.passwordn where n is the entry number, Finally, open the entry using this:

mkstore -wrl /home/mseibt/pstore -viewEntry oracle.security.client.connect_string1 ( <name obtained> in step 5)

7) Modifying entry values:

mkstore -wrl /home/mseibt/pstore -modifyEntry oracle.security.client.password1 newpass

Known Issues:

Issues 1 : Oracle Wallet Cannot Be Created using mkstore (Doc ID 951276.1)

SOLUTION

1. Stop the Database

2. cd $ORACLE_HOME/bin

3. relink all

4. mkstore -wrl $ORACLE_HOME/admin/wallet -create

Reference :

Using The Secure External Password Store (Doc ID 340559.1)

Wednesday, May 8, 2024

Changing max_string_size to extended for Oracle Pluggable database

Recently we have been reported "ORA-00910:specified length too long for its datatype" by application team . Upon checking we planned to upgrade MAX_STRING_SIZE to EXTENDED.

We cant set only at pdb level too and changes are replicated to standby through redo logs if changes are done only at PDB .

We will be changing MAX_STRING_SIZE only at pdb level

In order to expand the maximum value of varchar2 (also nvarchar2 and raw) datatypes in Oracle 12c and beyond, the max_string_size parameter needs to be set to "extended". This will change the maximum value from 4k (4096) to 32k (32767).

WARNING: You MUST run utl32k.sql immediately after changing max_string_size=extended, else you risk invalidating the database columns.

Notes :

1) The COMPATIBLE initialization parameter must be set to 12.0.0.0 or higher to set MAX_STRING_SIZE = EXTENDED.

2) The utl32k.sql script increases the maximum size of the VARCHAR2, NVARCHAR2, and RAW columns for the views where this is required. The script does not increase the maximum size of the VARCHAR2, NVARCHAR2, and RAW columns in some views because of the way the SQL for those views is written.

3) When the 32k varchar2 feature is enabled, then any function based indexes that rely on PL/SQL functions returning a varchar2 will become unusable when the utl32k.sql script is run. Such indexes will subsequently have to be dropped and it will not be possible to re-create them. Any attempt to recreate such an index will fail with ORA-1450. The reason for this is that such functional indexes will have a "key" size of 32k and this is larger than the maximum allowed key size. Prior to enabling the 32k varchar2 feature, such indexes would have had a key size of 4000 bytes, which is within the allowed limit for an index key.

4) In some cases

Running the rdbms/admin/utl32k.sql script may cause the below error:

a-ORA-14415: index in partially dropped state, submit DROP INDEX

This is caused by BUG 21450985 - ORA-14415: INDEX IN PARTIALLY DROPPED STATE, SUBMIT DROP INDEXSev 1 24X7 SR

b-ORA-30556: either functional or bitmap join index is defined on the column to be modified

This is caused by Bug 20539050 - ORA-30556 ON USING /RDBMS/ADMIN/UTL32K

Both the bugs are fixed in 12.2 version.For earlier versions one off patch can be requested by creating a SR to Oracle Support.

c-ORA-02019 WHEN RUNNING @?/RDBMS/ADMIN/UTL32K.SQL ON mview with private DB link

This is caused by BUG 19063812 - ORA-02019 WHEN RUNNING @?/RDBMS/ADMIN/UTL32K.SQL ON MV WITH PRIVATE DB LINK

It is fixed in 12.2.

Steps :

1) Purge recyclebin in pdb

1) Take pre snap of invalid Objects in pdb

2) Shut down the PDB abd restart in upgrade mode

alter pluggable database PDB1 close immediate instances=all ;

ALTER PLUGGABLE DATABASE pdb-name OPEN UPGRADE;

3) Change the setting of MAX_STRING_SIZE in the PDB to EXTENDED.

alter system set MAX_STRING_SIZE=EXTENDED sid='*';

@?/rdbms/admin/utl32k.sql

Note:

The utl32k.sql script increases the maximum size of the VARCHAR2, NVARCHAR2, and RAW columns for the views where this is required.

The script does not increase the maximum size of the VARCHAR2, NVARCHAR2, and RAW columns in some views because of the way the SQL for those views is written.

Run the rdbms/admin/utlrp.sql script in the PDB to recompile invalid objects. You must be connected AS SYSDBA to run the script.

4) Reopen the PDB in NORMAL mode

alter pluggable database PDB1 close immediate instances=all ;

ALTER PLUGGABLE DATABASE pdb-name OPEN ;

Verify client connectivity using service .

5) Compile Invalid Objects .

Generate post snap of invalid objects and compare with pre snap taken in step 1

6) Replicating to Standby :

Since we are changing at PDB level , changes should replicate to standby through archive logs .

Try to open in mount state temporarily and then normalize in read only mode after sometime .

Views :

select NAME,VALUE,ISPDB_MODIFIABLE,CON_ID from v$system_parameter where upper(NAME)='MAX_STRING_SIZE';

Reference :

https://docs.oracle.com/en/database/oracle/oracle-database/19/refrn/MAX_STRING_SIZE.html

Effect of Max_String_Size on Data guard (Doc ID 2010497.1)

How to Increase the Maximum Size of VARCHAR2, NVARCHAR2, and RAW Columns in 12C Database using MAX_STRING_SIZE ? (Doc ID 1570297.1)

Alter Pluggable Database Close Instances=ALL Not Working (Doc ID 2062080.1)