Oracle Background Processes that can be restarted and How to prioritize an Oracle Database background process

 

Thought of  documenting  this as at times we come across situations where w have to kill certain background process to high load  or other issues . 

This is only for information purpose . Its advisable to  check with  Oracle Support for any actions 

Killable:
ARCn: Redo log archivers
CJQn: Job scheduler coordinator
Dnnn: Dispatchers
DIA0: Diagnosibility process 0
DIAG: Diagnosibility coordinator
FDBA: Flashback data archiver process
Jnnn: Job scheduler processes
MMNL: Manageability Monitor Process 2
MMON: Manageability Monitor Process
PING: Interconnect latency measurement
Qnnn: Queue cleanup processes
QMNC: Queue coordinator
RECO: Distributed recovery process
Snnn: Shared servers
SMCO: Space management coordinator
Wnnn: Space management processes

Instance-Critical:
ACMS: Atomic controlfile to memory server
CKPT: Checkpoint
DBRM: Resource manager process
DBWn: Database writer processes
LGWR: Redo log writer
LMDn: Global enqueue service daemons
LMON: Global enqueue service monitor
MMAN: Memory manager
PMON: Process monitor
PSPn: Process spawners
RMSn: RAC management server
RVWR: Recovery writer
SMON: System monitor process
VKTM: Virtual keeper of time process

Increasing Priority of Background process . 

In   Test case we  will be increasing priority of LGWR  proces to get rid of log file snc wait . 

Increasing the LGWR priority is putting the LGWR process in the Round-Robin (SCHED_RR) class. You can increase process’s priority both using OS (renice, nice commands) or Database methods, but this post is about setting the priority using ‘_high_priority_process’ an undocumented/hidden parameter that prioritizes your database managed processes

starting from 21.3.0.0.0 LGWR process is part of _high_priority_processes group along with VKTM & LMS* processes.

Note: This being a hidden/undocumented parameter I advise to consult with Oracle support before going and changing the parameter value. 

 select ksppstvl from x$ksppi join x$ksppcv using (indx) where ksppinm='_high_priority_processes';

alter system set "_high_priority_processes"='LMS*|VKTM|LGWR' scope=spfile;

Restart the database

srvctl stop database -d abdul1

srvctl start database -d abdul2 

 select ksppstvl from x$ksppi join x$ksppcv using (indx) where ksppinm='_high_priority_processes';