LMS and Real Time Priority in Oracle RAC 10g and 11g (文档 ID 558185.1)

Applies to:

Oracle Database Backup Service - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Cloud Service - Version N/A and later
Oracle Database - Enterprise Edition - Version 10.2.0.3 and later
Oracle Database Cloud Schema Service - Version N/A and later
Linux x86
HP-UX PA-RISC (64-bit)
Oracle Solaris on SPARC (64-bit)
HP-UX Itanium
Linux x86-64
Linux Itanium
Oracle Real Application Clusters (RAC)

Purpose

The purpose of this bulletin is to introduce the fact that starting with 10.2.0.3 certain processes (lms*) runs by default in real time priority.

Scope

On Unix platforms -- like Linux, Solaris, HP -- the LMS process runs in Realtime mode. In versions prior to 10.2.0.3, LMS processes ran in the Time Sharing (TS) class

Details

1. On most platforms, LMS runs in Realtime mode starting with 10.2.0.3. This is normal behavior.
2. Customers should ensure that the number of realtime lms processes to be at least one less than the number of CPUs (cores) in the system. For example, if there are 4 instances of the DB on a node with 8 CPUs, then Customer should ensure that the sum of the LMS* processes on the instances is not more than 7.  The number of LMS* processes is determined / controlled by the initialization parameter GCS_SERVER_PROCESSES
3. In general, do not change the default number of LMS processes unless you are facing #2.
4. On some platforms, LMS runs in higher priority and not necessarily in Realtime mode. It is not recommended to change the default priority unless advised by Oracle Support.

In 18.x and above please refer to:  LMS process priority not showing correctly in 18.1+ versions (Doc ID 2613049.1) and LMS Processes Not Running In Real Time Mode (Doc ID 1310164.1)

References

NOTE:1310164.1 - LMS Processes Not Running In Real Time Mode
NOTE:948456.1 - Pre 11.2 Database Issues in 11gR2 Grid Infrastructure Environment
NOTE:1392248.1 - Auto-Adjustment of LMS Process Priority in Oracle RAC with 11.2.0.3 and later
NOTE:2613049.1 - LMS process priority not showing correctly in 18.1+ versions