Alert Log Recommendation - "Increase per process memlock (soft) limit to at least <n>MB to lock <n>% of SHARED GLOBAL AREA (SGA) pages into physical memory"
(Doc ID 2049901.1)
Last updated on AUGUST 25, 2023
Applies to:
Oracle Database - Standard Edition - Version 12.1.0.2 to 12.1.0.2 [Release 12.1]Oracle Database Cloud Schema Service - Version N/A and later
Gen 1 Exadata Cloud at Customer (Oracle Exadata Database Cloud Machine) - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Backup Service - Version N/A and later
Information in this document applies to any platform.
Symptoms
When starting Oracle 12c database, the alert log reports a recommendation to increase the per process memlock (soft) limit, e.g.:
Wed Aug 12 09:26:27 2015
Starting ORACLE instance (normal) (OS id: 14753)
...
Wed Aug 12 09:26:27 2015
Expected per process system memlock (soft) limit to lock
SHARED GLOBAL AREA (SGA) into memory: 4096M
Wed Aug 12 09:26:27 2015
Available system pagesizes:
4K, 2048K
Wed Aug 12 09:26:27 2015
Supported system pagesize(s):
Wed Aug 12 09:26:27 2015
PAGESIZE AVAILABLE_PAGES EXPECTED_PAGES ALLOCATED_PAGES ERROR(s)
Wed Aug 12 09:26:27 2015
4K Configured 1048581 1048581 NONE
Wed Aug 12 09:26:27 2015
Reason for not supporting certain system pagesizes:
Wed Aug 12 09:26:27 2015
2048K - Dynamic allocate and free memory regions
Wed Aug 12 09:26:27 2015
RECOMMENDATION: <==============================================
Wed Aug 12 09:26:27 2015
1. Increase per process memlock (soft) limit to at least 4096MB
to lock 100% of SHARED GLOBAL AREA (SGA) pages into physical memory
Starting ORACLE instance (normal) (OS id: 14753)
...
Wed Aug 12 09:26:27 2015
Expected per process system memlock (soft) limit to lock
SHARED GLOBAL AREA (SGA) into memory: 4096M
Wed Aug 12 09:26:27 2015
Available system pagesizes:
4K, 2048K
Wed Aug 12 09:26:27 2015
Supported system pagesize(s):
Wed Aug 12 09:26:27 2015
PAGESIZE AVAILABLE_PAGES EXPECTED_PAGES ALLOCATED_PAGES ERROR(s)
Wed Aug 12 09:26:27 2015
4K Configured 1048581 1048581 NONE
Wed Aug 12 09:26:27 2015
Reason for not supporting certain system pagesizes:
Wed Aug 12 09:26:27 2015
2048K - Dynamic allocate and free memory regions
Wed Aug 12 09:26:27 2015
RECOMMENDATION: <==============================================
Wed Aug 12 09:26:27 2015
1. Increase per process memlock (soft) limit to at least 4096MB
to lock 100% of SHARED GLOBAL AREA (SGA) pages into physical memory
As per /etc/security/limits.conf, the current settings are:
oracle soft memlock 1048576
oracle hard memlock 1048576
oracle hard memlock 1048576
The actual memory configuration shows values like:
NAME VALUE
--------------------------------------------- --------------------
...
memory_max_target 4294967296 <-------- 4G
memory_target 4294967296 <-------- 4G
object_cache_max_size_percent 10
object_cache_optimal_size 102400
olap_page_pool_size 0
result_cache_max_size 10747904
sga_max_size 4294967296 <-------- 4G
sga_target 0
shared_pool_reserved_size 25165824
shared_pool_size 0
streams_pool_size 0
...
--------------------------------------------- --------------------
...
memory_max_target 4294967296 <-------- 4G
memory_target 4294967296 <-------- 4G
object_cache_max_size_percent 10
object_cache_optimal_size 102400
olap_page_pool_size 0
result_cache_max_size 10747904
sga_max_size 4294967296 <-------- 4G
sga_target 0
shared_pool_reserved_size 25165824
shared_pool_size 0
streams_pool_size 0
...
And the actual startup values are:
PARM SESSVAL INSTVAL
---------------------------------------- --------------- ---------------
__shared_pool_size 503316480 503316480 <-------- 480M
__large_pool_size 33554432 33554432
__java_pool_size 16777216 16777216
__streams_pool_size 0 0
_kghdsidx_count 1 1
_ksmg_granule_size 16777216 16777216
__sga_target 2566914048 2566914048 <-------- 2.3G
_memory_imm_mode_without_autosga TRUE TRUE
__db_cache_size 1879048192 1879048192 <-------- 1.75G
__pga_aggregate_target 1728053248 1728053248 <-------- 1.6G
---------------------------------------- --------------- ---------------
__shared_pool_size 503316480 503316480 <-------- 480M
__large_pool_size 33554432 33554432
__java_pool_size 16777216 16777216
__streams_pool_size 0 0
_kghdsidx_count 1 1
_ksmg_granule_size 16777216 16777216
__sga_target 2566914048 2566914048 <-------- 2.3G
_memory_imm_mode_without_autosga TRUE TRUE
__db_cache_size 1879048192 1879048192 <-------- 1.75G
__pga_aggregate_target 1728053248 1728053248 <-------- 1.6G
Changes
Cause
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In this Document
Symptoms |
Changes |
Cause |
Solution |
References |