Pythian Blog: Technical Track

Enabling large pages on Oracle Database 11g running on IBM AIX

by Pythian Marketing on Apr 4, 2016 12:00:00 AM

For implementing Large Pages on AIX first you will need to choose large page size at OS level. On AIX you can have multiple large page sizes of 4KB, 64KB, 16MB, and 16GB. In this example we will be using a large page size of 16MB. Steps for implemenatation: 1- Based on MOS Doc ID 372157.1 first you need to enable Large Pages at OS level [code lang="bash"] # vmo -r -o lgpg_size=16777216 -o lgpg_regions=<Total number of pages> # vmo -o lru_file_repage=0 # vmo -p -o v_pinshm=1 # lsuser -a capabilities oracle # chuser capabilities=CAP_BYPASS_RAC_VMM,CAP_PROPAGATE oracle # bosboot -a [/code] This needs a server reboot For complete instruction please review note ID 372157.1 2- Setting parameters at instance level On AIX databases you only need to set LOCK_SGA to TRUE: [code lang="bash"] alter system set lock_sga=TRUE scope=spfile; [/code] Note: On AIX databases, USE_LARGE_PAGES parameter has NO impact. These parameters are only valid for databases running on Linux, the value of this parameter even if set to FALSE will be ignored on AIX. By default when Large Pages is available on AIX it will be used by database instances regardless of USE_LARGE_PAGES parameter value. You only need to set LOCK_SGA. 3- Restart the instance and confirm Large Pages is in use: After setting lock_sga instance must be restarted. As I explained above, when Large Pages is available at OS level it will be used by instance, but the key point in here is how to confirm whether Large Pages is in use or not. How to check if Huge Pages is used by Oracle instance. For Oracle 11g running on AIX, no informational message is written to the alert log as what we see in the alert log of databases running on Linux. So for your database instance running on AIX do NOT expect following lines in the alert log: ****************** Large Pages Information ***************** Total Shared Global Region in Large Pages = xx MB (100%) Large Pages used by this instance: xxx (xxx MB) Large Pages unused system wide = x (xxx MB) (alloc incr 4096 KB) Large Pages configured system wide = xxx (xxx MB) Large Page size = 16 MB *********************************************************** The only way you can make sure large pages is being used by instance is checking memory usage at OS level: Consider SGA_TARGET in your instance is 8G Total number of Large Pages (with size of 16M) will be 8G/16M + 1 which is : 8589934592 / 16777216 + 1 = 513 Check the number of large 16M pages in use at OS level before starting your instance: [code lang="bash"] $ vmstat -P all System configuration: mem=98304MB pgsz memory page ----- -------------------------- ------------------------------------ siz avm fre re pi po fr sr cy 4K 4420992 2926616 487687 0 0 5 1280 2756 0 64K 582056 581916 754 0 0 0 0 0 0 16M 2791 87 2704 0 0 0 0 0 0 [/code] In this example number of 16M pages in use before starting instance is 87 pages from total available of 2791 pages. We start the instance with SGA size of 8G: [code lang="bash"] SQL> startup ORACLE instance started. Total System Global Area 8551575552 bytes Fixed Size 2238616 bytes Variable Size 2348812136 bytes Database Buffers 6190792704 bytes Redo Buffers 9732096 bytes Database mounted. Database opened. SQL> show parameter sga_target NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ sga_target big integer 8G SQL> show parameter lock_sga NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ lock_sga boolean TRUE [/code] Then we check Large pages in use again : [code lang="bash"] $ vmstat -P all System configuration: mem=98304MB pgsz memory page ----- -------------------------- ------------------------------------ siz avm fre re pi po fr sr cy 4K 4428160 2877041 420004 0 0 5 1279 2754 0 64K 581608 530522 51695 0 0 0 0 0 0 16M 2791 600 2191 0 0 0 0 0 0 [/code] As you can see the total number of 16M pages in use is now 600 pages, which is exactly 513 pages more than what it was before instance startup. This proves that 16M pages have been used by our instance. You can also check memory usage of your instance by checking one of the instance processes like pmon: [code lang="bash"] $ ps -ef|grep pmon oracle 14024886 31392176 0 14:05:34 pts/0 0:00 grep pmon oracle 41681022 1 0 Mar 11 - 3:12 ora_pmon_KBS [/code] Then check memory used by this process is from 16M Pages: [code lang="bash"] $ svmon -P 41681022 ------------------------------------------------------------------------------- Pid Command Inuse Pin Pgsp Virtual 64-bit Mthrd 16MB 41681022 oracle 2180412 2109504 1778 2158599 Y N Y PageSize Inuse Pin Pgsp Virtual s 4 KB 31820 0 1650 9975 m 64 KB 2959 516 8 2961 L 16 MB 513 513 0 513 [/code] I hope this will be useful for you, and good luck.
Topics: MySQL AWS Technical Track Cloud RDS Automatic Backups Read Replica Binary Logging

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