不管是AIX平臺還是在Linux平臺使用大頁記憶體（Large Page Memory）都是依賴於作業系統的特性。Linux平臺和AIX平臺預設的頁面大小都是4K，Linux平臺的HugePage特性通常每個頁面可以調整為2M；AIX平臺的Large Page Memory使得單個頁面最大可以調整為16M；下面詳細討論在AIX平臺下，Oracle資料庫例項使用64K和16M兩種規格的記憶體頁面，主要討論的是16M的記憶體頁面。

1.使用64K記憶體頁面
在oracle使用者的PROFILE檔案中加入以下環境變數的設定：
export
在使以上環境變數生效的情況下重啟Oracle資料庫例項。

使用前：
halpar1:[/home/oracle]$ps -efZ | grep ora
oracle 340174 1 0 22:27:07 - 0:00 4K 4K 4K 4K ora_mmnl_ordb
oracle 405740 1 0 22:27:27 - 0:00 4K 4K 4K 4K ora_q001_ordb
oracle 409848 1 1 22:27:07 - 0:00 4K 4K 4K 4K ora_ckpt_ordb
oracle 463038 1 0 22:27:06 - 0:00 4K 4K 4K 4K ora_lgwr_ordb
oracle 499916 704560 0 22:26:57 pts/0 0:00 4K 4K 4K 4K -ksh
oracle 508116 1 0 22:27:06 - 0:00 4K 4K 4K 4K ora_dbw0_ordb
oracle 524472 1 0 22:27:06 - 0:00 4K 4K 4K 4K ora_mman_ordb
oracle 549010 1 0 22:27:06 - 0:00 4K 4K 4K 4K ora_psp0_ordb
oracle 577616 1 0 22:27:06 - 0:00 4K 4K 4K 4K ora_pmon_ordb
oracle 589946 1 0 22:27:07 - 0:00 4K 4K 4K 4K ora_smon_ordb

使用後：
halpar1:[/]#ps -efZ | grep ora
oracle 340180 1 0 22:43:02 - 0:00 64K 64K 64K 4K ora_psp0_ordb
oracle 405742 1 0 22:43:22 - 0:00 64K 64K 64K 4K ora_q000_ordb
oracle 409850 1 0 22:43:03 - 0:00 64K 64K 64K 4K ora_d000_ordb
oracle 463040 1 0 22:43:03 - 0:00 64K 64K 64K 4K ora_mmnl_ordb
oracle 499916 704560 0 22:26:57 pts/0 0:00 4K 4K 4K 4K -ksh
oracle 508118 1 0 22:43:03 - 0:00 64K 64K 64K 4K ora_mmon_ordb
oracle 524474 1 15 22:43:03 - 0:00 64K 64K 64K 4K ora_cjq0_ordb
oracle 549012 1 0 22:43:02 - 0:00 64K 64K 64K 4K ora_reco_ordb
oracle 577618 1 0 22:43:02 - 0:00 64K 64K 64K 4K ora_smon_ordb
oracle 589948 1 0 22:43:02 - 0:00 64K 64K 64K 4K ora_ckpt_ordb

2.使用16M記憶體頁面

1).在作業系統執行如下命令：
#vmo -po v_pinshm=1
#vmo -po maxpin%=80（根據實際需要來設定）
#chuser capabilities=CAP_BYPASS_RAC_VMM,CAP_PROPAGATE oracle（使用lsuser -a capabilities oracle命令可以檢視oracle使用者設定的此屬性）
#vmo -po lgpg_size=16777216 -o lgpg_regions=64（16777216=16M*64=1024M記憶體，lgpg_size根據實際的記憶體和資料庫例項SGA的大小來設定）
Setting lgpg_size to 16777216 in nextboot file
Setting lgpg_regions to 64 in nextboot file
Warning :although the change concerns a dynamic ...
optimally restore these settings at reboot（建議做bosboot,並且重新啟動作業系統）
Setting lgpg_size to 16777216
Setting lgpg_regions to 64
#bosboot -a

注意：Oracle Database 10.2.0.4及其以上的版本必須完成chuser capabilities=CAP_BYPASS_RAC_VMM,CAP_PROPAGATE oracle命令對oracle作業系統使用者屬性的設定，如果不設定可能導致出現如下文章中的問題：http://space.itpub.net/23135684/viewspace-631065

執行下面的命令可以去除16M的頁面設定：
#vmo -po lgpg_size=0 -o lgpg_regions=0

2).需要修改oracle使用者的profile檔案
#export ORACLE_SGA_PGSZ=16M

Oracle 10.2.0.4,需要設定這個引數，參見metalink DOC ID:NOTE:728444.1

3).需要修改資料庫引數
執行以下的SQL語句，主要設定LOCK_SGA為true：
SQL> alter system set pre_page_sga=true scope=spfile;
SQL> alter system set lock_sga=true scope=spfile;
將LOCK_SGA設定為TRUE會觸發Oracle資料庫例項使用Large Page Memory，設定之後重啟資料庫例項。

使用16M記憶體頁面之前：
halpar1:[/]#svmon
size inuse free pin virtual
memory 1048576 637640 447815 445323 288587
pg space 262144 2841
work pers clnt other
pin 109892 0 2849 70438
in use 288587 0 86909
PageSize PoolSize inuse pgsp pin virtual
s 4 KB - 245336 2841 102907 158427
m 64 KB - 8135 0 5017 8135
L 16 MB 64 0 0 64 0（值為0）

使用16M記憶體頁面之後：
halpar1:[/]#svmon
size inuse free pin virtual
memory 1048576 691573 393883 446308 473636
pg space 262144 3088
work pers clnt other
pin 241949 0 2849 70438
in use 473636 0 86865
PageSize PoolSize inuse pgsp pin virtual
s 4 KB - 247605 3088 102916 160740
m 64 KB - 11364 0 5078 11364
L 16 MB 64 32 0 64 32（值為非0）

如果資料庫被升級到了10.2.0.4或者10.2.0.5，經過以上配置預設可能也不會使用到大頁，請參考文章：《AIX: Upgraded To 10.2.0.4 (or 10.2.0.5) And Large Page Memory Is No Longer Used [ID 728444.1] 》 http://space.itpub.net/?uid-23135684-action-viewspace-itemid-742754

有關在AIX平臺使用Large Page Memory的詳細內容參考文章：《How to enable Large Page Feature on AIX-Based Systems [ID 372157.1]》http://space.itpub.net/?uid-23135684-action-viewspace-itemid-742753

結合METALINK的文章，AIX平臺下的16M Large Page Memory配置如下：

# oslevel -s

6100-07-05-1228

# vmo -L v_pinshm

NAME CUR DEF BOOT MIN MAX UNIT TYPE

DEPENDENCIES

--------------------------------------------------------------------------------

v_pinshm 0 0 0 0 1 boolean D

--------------------------------------------------------------------------------

# vmo -po v_pinshm=1

Setting v_pinshm to 1 in nextboot file

Setting v_pinshm to 1

# vmo -L v_pinshm

NAME CUR DEF BOOT MIN MAX UNIT TYPE

DEPENDENCIES

--------------------------------------------------------------------------------

v_pinshm 1 0 1 0 1 boolean D

--------------------------------------------------------------------------------

# vmo -L maxpin%

NAME CUR DEF BOOT MIN MAX UNIT TYPE

DEPENDENCIES

--------------------------------------------------------------------------------

maxpin% 80 80 80 1 100 % memory D

pinnable_frames

memory_frames

--------------------------------------------------------------------------------

# lsuser -a capabilities oracle

oracle capabilities=CAP_BYPASS_RAC_VMM,CAP_PROPAGATE,CAP_NUMA_ATTACH

# lsuser -a capabilities grid

grid capabilities=CAP_BYPASS_RAC_VMM,CAP_PROPAGATE,CAP_NUMA_ATTACH

# lsattr -El mem0

ent_mem_cap I/O memory entitlement in Kbytes False

goodsize 31488 Amount of usable physical memory in Mbytes False

mem_exp_factor Memory expansion factor False

size 31488 Total amount of physical memory in Mbytes False

var_mem_weight Variable memory capacity weight False

# vmo -p -o lgpg_regions=1024 -o lgpg_size=16777216

Setting lgpg_size to 16777216 in nextboot file

Setting lgpg_regions to 1024 in nextboot file

Warning: although the change concerns a dynamic tunable, bosboot should be run to optimally restore these settings at reboot

Setting lgpg_size to 16777216

Setting lgpg_regions to 1024

# vmo -o lru_file_repage=0

Setting lru_file_repage to 0

Warning: a restricted tunable has been modified

# bosboot -a

bosboot: Boot image is 51228 512 byte blocks.

# vmstat -l

System configuration: lcpu=16 mem=31488MB

kthr memory page faults cpu large-page

----- ----------- ------------------------ ------------ ----------- -----------

r b avm fre re pi po fr sr cy in sy cs us sy id wa alp flp

1 1 899643 7522 0 0 0 47 63 0 21 2107 579 0 0 99 0 0 1024

# svmon

size inuse free pin virtual mmode

memory 8060928 8042431 18497 4724020 902447 Ded

pg space 2621440 3418

work pers clnt other

pin 292772 0 0 236944

in use 902447 0 2945680

PageSize PoolSize inuse pgsp pin virtual

s 4 KB - 3372319 3418 310180 426639

m 64 KB - 29738 0 13721 29738

L 16 MB 1024 0 0 1024 0

下面是調整Oracle資料庫例項引數後使用Large Page Memory的過程：

$ sql

SQL*Plus: Release 11.2.0.3.0 Production on Thu Sep 6 15:00:51 2012

Connected to:

Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production

With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> alter system set sga_max_size=16g scope=spfile;

System altered.

SQL> alter system set sga_target=16g scope=spfile;

System altered.

SQL> alter system set pre_page_sga=true scope=spfile;

System altered.

SQL> alter system set lock_sga=true scope=spfile;

System altered.

SQL> shutdown immediate

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup nomount

ORA-27102: out of memory

IBM AIX RISC System/6000 Error: 12: Not enough space

伺服器總共有32G的記憶體，Large Page Memory設定的是16G，Oracle資料庫例項SGA設定的也是16G，但資料庫例項啟動的時候由於粒度的原因佔用的空間可能稍微大於16G，那麼Large Page Memory空間是不夠用的（這段空間自動分配之後就被佔據，不被任何程式使用，Oracle例項無法使用，空間即被浪費），剩餘的空間也是不夠的，所以報記憶體不足。解決辦法是將lgpg_regions增加1即可：

# vmo -p -o lgpg_regions=1025 -o lgpg_size=16777216

Setting lgpg_size to 16777216 in nextboot file

Setting lgpg_regions to 1025 in nextboot file

Warning: although the change concerns a dynamic tunable, bosboot should be run to optimally restore these settings at reboot

Setting lgpg_size to 16777216

Setting lgpg_regions to 1025

SQL> startup

ORACLE instance started.

Total System Global Area 1.7103E+10 bytes

Fixed Size 2238616 bytes

Variable Size 771753832 bytes

Database Buffers 1.6307E+10 bytes

Redo Buffers 21716992 bytes

Database mounted.

Database opened.

# svmon

size inuse free pin virtual mmode

memory 8060928 5732976 2327952 4683897 5139434 Ded

pg space 2621440 3736

work pers clnt other

pin 4446953 0 0 236944

in use 5139434 0 593542

PageSize PoolSize inuse pgsp pin virtual

s 4 KB - 1096480 3736 309289 502938

m 64 KB - 27381 0 11013 27381

L 16 MB 1025 1025 0 1025 1025

# vmstat -l

System configuration: lcpu=16 mem=31488MB

kthr memory page faults cpu large-page

----- ----------- ------------------------ ------------ ----------- -----------

r b avm fre re pi po fr sr cy in sy cs us sy id wa alp flp

1 1 5139300 2328085 0 0 0 0 0 0 18 1853 568 0 0 99 0 1025 0
從上面的命令可以看出1025個Large Page Memory都被使用了。

--end--

Oracle資料庫例項在AIX 平臺下使用大頁記憶體(Large Page Memory)

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