vmo

Misuse of this command can cause performance degradation or operating system failure.

Introduction

The vmo command manages AIX Virtual Memory tunable parameters and is part of the AIX fileset "bos.perf.tune".

Valid For

AIX 6.1

All Oracle databases that use filesystem storage (i.e. databases that do not use ASM)

Recommendations

IBM recommends the following Virtual Memory settings for use with programs which need to protect computational memory (like Oracle):

strict_maxperm=0 (default)

strict_maxclient=1 (default)

lru_file_repage=0

maxperm%=90

minperm%=5 (physical RAM <32 GB)

minperm%=10 (physical RAM >32 GB but <64 GB)

minperm%=20 (physical RAM >64 GB)

v_pinshm=1

maxpin%=percent_of_real_memory

(IBM does not recommend decreasing the maxpin% value. See the "Support for pinned memory" link in the References section below.)

Where "percent_of_real_memory" = ( (size of SGA / size of physical memory) *100) + 3

and

Set Oracle database parameter LOCK_SGA to TRUE in the pfile/spfile

and

Sum of all SGAs on the system do not exceed approximately 60% of physical memory

Setting of v_pinshm is only required for Oracle database version 9i and earlier which pins memory using shmget(IPC_PRIVATE, shm_size, IPC_CREAT|SHM_PIN). 10g and above uses a different method shmctl(shm_id, SHM_LOCK, ...)to pin memory that is no longer dependent on v_pinshm.

The parameter lru_file_repage no longer exists in AIX 6100-09

Bibliography

316533.1 - AIX: Database performance gets slower the longer the database is running

https://www.oracle.com/technetwork/database/clusterware/overview/rac-aix-system-stability-131022.pdf