[20190507]sga_target=0注意修改_kghdsidx_count设置.txt

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[20190507]sga_target=0注意修改_kghdsidx_count设置.txt --//昨天遇到一例视图定义太复杂导致长时间分析sql语句出现library cache lock等待事件的情况. --//加上大量使用非绑定变量语句,导致硬解析增加,导致问题更加严重. --//顺便解析当时同事发现仅仅1个CPU特别忙.实际上因为仅仅1个shared pool latch在工作. 1.环境: > @ ver1 PORT_STRING VERSION BANNER ------------------ -------------- ---------------------------------------------------------------- IBMPC/WIN_NT-8.1.0 10.2.0.3.0 Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - Prod --//注32位版本. 2.解析: SELECT addr ,latch# ,child# ,level# ,name ,gets ,sleeps ,immediate_gets ,immediate_misses ,spin_gets FROM V$LATCH_CHILDREN WHERE name LIKE 'shared pool' ORDER BY addr; ADDR LATCH# CHILD# LEVEL# NAME GETS SLEEPS IMMEDIATE_GETS IMMEDIATE_MISSES SPIN_GETS -------- ---------- ---------- ---------- ----------- ---------- ---------- -------------- ---------------- ---------- 05AA3858 213 1 7 shared pool 25235287 182 0 0 7384 05AA38C0 213 2 7 shared pool 151 0 0 0 0 05AA3928 213 3 7 shared pool 151 0 0 0 0 05AA3990 213 4 7 shared pool 151 0 0 0 0 05AA39F8 213 5 7 shared pool 151 0 0 0 0 05AA3A60 213 6 7 shared pool 151 0 0 0 0 05AA3AC8 213 7 7 shared pool 151 0 0 0 0 7 rows selected. --//仅仅1个shared pool latch在使用. > show parameter sga_ NAME TYPE VALUE ------------- ----------- ------ sga_max_size big integer 1200M sga_target big integer 1200M > @　hide _kghdsidx_count NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE --------------- ------------------ ---------------------- ---------------------- ---------------------- _kghdsidx_count max kghdsidx count TRUE 1 1 > @ hide _enable_shared_pool_durations NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE ----------------------------- -------------------------------------- ------------- ------------- ------------ _enable_shared_pool_durations temporary to disable/enable kgh policy TRUE TRUE TRUE > show parameter cpu_count NAME TYPE VALUE --------- ------- ------ cpu_count integer 16 --//注:在任务管理器看到32个CPU.不过我发现图中下面一排16个cpu好像没有负载. --//主要问题是参数_kghdsidx_count=1.仅仅1个subpool.看来这个版本按照每个子缓冲池至少为512MB设计的. --//参数_kghdsidx_count大小由CPU数量以及共享池大小决定的.最大不过7个. --//我仅仅知道的原则: --//共享子缓冲池的分配的算法很简单： --//·每个子缓冲池必须满足一定的内存约束； --//·每4颗CPU可以分配一个子缓冲池，最多7个。 --//本来oracle这样做为了减少shared pool,但是带来另外的问题,如果每个子池太小,反而出现ora-04031错误.于是oracle限制每个子池 --//的大小,你可以发现一些blog提到减少参数_kghdsidx_count大小,限制每个子池避免出现子池太小的情况. --//在Oracle 9i中，每个SubPool至少128MB，在Oracle 10g中，每个子缓冲池至少为256MB,在Oracle 11g中，每个子缓冲池至少为512MB. --//Oracle 10g会将单个缓冲池分割再细分4个子分区进行管理(这可能是因为通常4颗CPU才分配一个SubPool), --//分别是"instance", "session", "cursor", and "execution". --//对方安装32位系统,不能设置很大sga,受限共享内存大小600M上下,这样仅仅1个shared pool latch. --//这样在大量硬解析的情况下,特别在分析sql语句很长时间的情况下仅仅1个shared pool latch自然很忙. --//也就是同事看到的情况,仅仅1个CPU在忙...而且sql语句中的视图关联的表太多,导致1条sql语句消耗共享池很大,我执行前面的语句,查看 --//v$sqlarea的SHARABLE_MEM达到512K.这样大量非绑定变量语句导致许多对象退出又再进入共享池. --//这就好比一个宾馆的前台仅仅1名接待人员一样,客户入住登记少没有问题,一旦大量客户登记入住,1个人自然忙不过来, --//而其他人根本插不上手.有时候非常像现实工作的场景,1个忙的要死,别人根本插不上手,只能在那干等^_^. 3.突然想起我以前1个测试: --//[20190104]sga_target 的设置和ORA-04031错误.txt => http://blog.itpub.net/267265/viewspace-2305567/ --//发现一个问题,就是设置sga_target=0,如果大量语句不使用绑定变量可能存在问题.参数_kghdsidx_count=1,仅仅1个shared pool latch. --//这样情况应该适当增加_kghdsidx_count,通过测试说明问题: $ export ORACLE_SID=xxxx $ cat initxxxx.ora db_name=xxxx instance_name=xxxx sga_target=0 sga_max_size=20G --//设置sga_target=0. SYS@xxxx> startup nomount ORACLE instance started. Total System Global Area 2.1379E+10 bytes Fixed Size 2262656 bytes Variable Size 2.1206E+10 bytes Database Buffers 134217728 bytes Redo Buffers 36073472 bytes SELECT addr ,latch# ,child# ,level# ,name ,gets ,sleeps ,immediate_gets ,immediate_misses ,spin_gets FROM V$LATCH_CHILDREN WHERE name LIKE 'shared pool' ORDER BY addr; ADDR LATCH# CHILD# LEVEL# NAME GETS SLEEPS IMMEDIATE_GETS IMMEDIATE_MISSES SPIN_GETS ---------------- ---------- ---------- ---------- ----------- ---- ---------- -------------- ---------------- ---------- 000000006010F288 336 1 7 shared pool 1397 0 0 0 5 000000006010F328 336 2 7 shared pool 0 0 0 0 0 000000006010F3C8 336 3 7 shared pool 0 0 0 0 0 000000006010F468 336 4 7 shared pool 0 0 0 0 0 000000006010F508 336 5 7 shared pool 0 0 0 0 0 000000006010F5A8 336 6 7 shared pool 0 0 0 0 0 000000006010F648 336 7 7 shared pool 0 0 0 0 0 7 rows selected. SYS@xxxx> @ hide _kghdsidx_count old 10: and lower(a.ksppinm) like lower('%&1%') new 10: and lower(a.ksppinm) like lower('%_kghdsidx_count%') NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE --------------- ------------------ ------------- ------------- ------------ _kghdsidx_count max kghdsidx count TRUE 1 1 SYS@xxxx> @ hide _enable_shared_pool_durations old 10: and lower(a.ksppinm) like lower('%&1%') new 10: and lower(a.ksppinm) like lower('%_enable_shared_pool_durations%') NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE ----------------------------- -------------------------------------- ------------- ------------- ------------ _enable_shared_pool_durations temporary to disable/enable kgh policy TRUE FALSE FALSE --//注意_enable_shared_pool_durations参数,在sga_target=0的情况下,_enable_shared_pool_durations的缺省值等于FALSE(实际上设 --//置为true也无效,看后面测试) --//也就是仅仅1个subpool,下面仅仅一个子子池. SYS@xxxx> @ sgastatx.sql 'free memory' -- All allocations: SUBPOOL BYTES MB ------------------------------ ---------- ---------- shared pool (0 - Unused): 67108864 64 shared pool (1): 268435456 256 shared pool (Total): 335544320 320 -- Allocations matching "free memory": old 15: AND LOWER(ksmssnam) LIKE LOWER('%&1%') new 15: AND LOWER(ksmssnam) LIKE LOWER('%free memory%') SUBPOOL NAME SUM(BYTES) MB ------------------------------ -------------------- ---------- ---------- shared pool (0 - Unused): free memory 67108864 64 shared pool (1): free memory 30813880 29.39 --//仅仅1个子池.共享内存不足的情况下会从shared pool (0 - Unused)分过来. --//另外注意1个问题,有一些文章提示查询x$kghlu可以查询这些子缓冲池的分配,我的测试不行,当然我现在sga_target=0的情况下不存 --//在子子池的情况. --//通过一个内部表X$KGHLU([K]ernel [G]eneric memory [H]eap manager State of [L]R[U] Of Unpinned Recreatable chunks)可以 --//查询这些子缓冲池的分配： (我的测试不行!!) SYS@xxxx> select * from x$kghlu; ADDR INDX INST_ID KGHLUIDX KGHLUDUR KGHLUSHRPOOL KGHLUFSH KGHLUOPS KGHLURCR KGHLUTRN KGHLUMXA KGHLUMES KGHLUMER KGHLURCN KGHLURMI KGHLURMZ KGHLURMX KGHLUNFU KGHLUNFS ---------------- ---------- ---------- ---------- ---------- ------------ ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- 00007F6D32E5EFF0 0 1 1 0 1 0 64 3 43 2147483647 0 0 0 0 0 0 0 0 --//只能通过heapdump转储获取这方面信息. SYS@xxxx> alter session set events 'immediate trace name heapdump level 2'; Session altered. $ grep 'sga heap' /u01/app/oracle/diag/rdbms/xxxx/xxxx/trace/xxxx_ora_43866.trc HEAP DUMP heap name="sga heap" desc=0x60001190 HEAP DUMP heap name="sga heap(1,0)" desc=0x6005c318 --//可以看出问题.仅仅1个子池,不细分子子池.也就是在sga_target=0的情况下,可能需要手工设置_kghdsidx_count的大小. --//不然可能出现shared pool latch的争用,特别在应用没有绑定变量的情况下. --//我个人建议sga_target=0的情况下手工设置shared_pool_size,db_cache_size. --//或者sga_target<>0的情况下,也设置shared_pool_size,db_cache_size作为最小值,避免内存在这些组件中变换. --//修改*._kghdsidx_count=3 $ cat initxxxx.ora db_name=xxxx instance_name=xxxx #sga_target=20G sga_target=0 sga_max_size=20G #pre_page_sga=true *._kghdsidx_count=3 SYS@xxxx> startup nomount ORA-04031: unable to allocate 320032 bytes of shared memory ("shared pool","unknown object","KGSK scheduler","KGSK chg class latches") --//shared_pool_size太小.仅仅320M. --//测试增加*._kghdsidx_count=3,*.shared_pool_size=1600M,*._enable_shared_pool_durations=true的情况: $ cat initxxxx.ora db_name=xxxx instance_name=xxxx sga_target=0G #sga_target=20G sga_max_size=20G #pre_page_sga=true *._kghdsidx_count=3 *.shared_pool_size=1600M *._enable_shared_pool_durations=true ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SYS@xxxx> startup nomount ORACLE instance started. Total System Global Area 2.1379E+10 bytes Fixed Size 2262656 bytes Variable Size 2.1206E+10 bytes Database Buffers 134217728 bytes Redo Buffers 36073472 by SYS@xxxx> @ hide _kghdsidx_count old 10: and lower(a.ksppinm) like lower('%&1%') new 10: and lower(a.ksppinm) like lower('%_kghdsidx_count%') NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE --------------- ------------------ ------------- ------------- ------------ _kghdsidx_count max kghdsidx count FALSE 3 3 SYS@xxxx> @ hide _enable_shared_pool_durations old 10: and lower(a.ksppinm) like lower('%&1%') new 10: and lower(a.ksppinm) like lower('%_enable_shared_pool_durations%') NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE ---------------------------------------- -------------------------------------- ------------- ------------- ------------ _enable_shared_pool_durations temporary to disable/enable kgh policy FALSE TRUE TRUE SYS@xxxx> select * from x$kghlu; ADDR INDX INST_ID KGHLUIDX KGHLUDUR KGHLUSHRPOOL KGHLUFSH KGHLUOPS KGHLURCR KGHLUTRN KGHLUMXA KGHLUMES KGHLUMER KGHLURCN KGHLURMI KGHLURMZ KGHLURMX KGHLUNFU KGHLUNFS ---------------- ---------- ---------- ---------- ---------- ------------ ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- 00007FC432A52F70 0 1 3 0 1 0 20 0 14 2147483647 0 0 0 0 0 0 0 0 00007FC432A54640 1 1 2 0 1 0 9 0 7 2147483647 0 0 0 0 0 0 0 0 00007FC432A53FF0 2 1 1 0 1 0 14 0 10 2147483647 0 0 0 0 0 0 0 0 --//仅仅3个子池.看不出子子池. SYS@xxxx> alter session set events 'immediate trace name heapdump level 2'; Session altered. $ grep 'sga heap' /u01/app/oracle/diag/rdbms/xxxx/xxxx/trace/xxxx_ora_43949.trc HEAP DUMP heap name="sga heap" desc=0x60001190 HEAP DUMP heap name="sga heap(1,0)" desc=0x6005c318 HEAP DUMP heap name="sga heap(2,0)" desc=0x60065be0 HEAP DUMP heap name="sga heap(3,0)" desc=0x6006f4a8 --//可以发现设置即使_enable_shared_pool_durations=TRUE,在sga_target=0G的情况下也不会出现子子池的情况. SYS@xxxx> @ sgastatx.sql 'free memory' -- All allocations: SUBPOOL BYTES MB ------------------------------ ---------- ---------- shared pool (0 - Unused): 1275068416 1216 shared pool (1): 134217728 128 shared pool (2): 134217728 128 shared pool (3): 134217728 128 shared pool (Total): 1677721600 1600 -- Allocations matching "free memory": old 15: AND LOWER(ksmssnam) LIKE LOWER('%&1%') new 15: AND LOWER(ksmssnam) LIKE LOWER('%free memory%') SUBPOOL NAME SUM(BYTES) MB ------------------------------ ---------------------------------------- ---------- ---------- shared pool (0 - Unused): free memory 1275068416 1216 shared pool (1): free memory 48797608 46.54 shared pool (2): free memory 34835672 33.22 shared pool (3): free memory 48306064 46.07 SELECT addr ,latch# ,child# ,level# ,name ,gets ,sleeps ,immediate_gets ,immediate_misses ,spin_gets FROM V$LATCH_CHILDREN WHERE name LIKE 'shared pool' ORDER BY addr; ADDR LATCH# CHILD# LEVEL# NAME GETS SLEEPS IMMEDIATE_GETS IMMEDIATE_MISSES SPIN_GETS ---------------- ---------- ---------- ---------- ----------- ---- ---------- -------------- ---------------- ---------- 000000006010F288 336 1 7 shared pool 732 0 1 0 0 000000006010F328 336 2 7 shared pool 673 0 1 0 0 000000006010F3C8 336 3 7 shared pool 903 0 1 0 1 000000006010F468 336 4 7 shared pool 1 0 0 0 0 000000006010F508 336 5 7 shared pool 1 0 0 0 0 000000006010F5A8 336 6 7 shared pool 1 0 0 0 0 000000006010F648 336 7 7 shared pool 1 0 0 0 0 7 rows selected. --//总之,如果手工管理内存,设置sga_target=0G的情况下,适当设置_kghdsidx_count,shared_pool_size,db_cache_size值. 4.最后测试sga_target<>0的情况: $ grep -v "^#" initxxxx.ora db_name=xxxx instance_name=xxxx sga_target=20G sga_max_size=20G SYS@xxxx> @ hide _kghdsidx_count old 10: and lower(a.ksppinm) like lower('%&1%') new 10: and lower(a.ksppinm) like lower('%_kghdsidx_count%') NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE ---------------------------------------- --------------------------------------- ------------- ------------- ------------ _kghdsidx_count max kghdsidx count TRUE 6 6 SYS@xxxx> @ hide _enable_shared_pool_durations old 10: and lower(a.ksppinm) like lower('%&1%') new 10: and lower(a.ksppinm) like lower('%_enable_shared_pool_durations%') NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE ---------------------------------------- --------------------------------------- ------------- ------------- ------------ _enable_shared_pool_durations temporary to disable/enable kgh policy TRUE TRUE TRUE SYS@xxxx> @ sgastatx.sql 'free memory' -- All allocations: SUBPOOL BYTES MB ------------------------------ ---------- ---------- shared pool (0 - Unused): 469762048 448 shared pool (1): 268435456 256 shared pool (2): 335544320 320 shared pool (3): 335544320 320 shared pool (4): 335544320 320 shared pool (5): 268435456 256 shared pool (6): 335544320 320 shared pool (Total): 2348810240 2240 8 rows selected. -- Allocations matching "free memory": old 15: AND LOWER(ksmssnam) LIKE LOWER('%&1%') new 15: AND LOWER(ksmssnam) LIKE LOWER('%free memory%') SUBPOOL NAME SUM(BYTES) MB ------------------------------ -------------------- ---------- ---------- shared pool (0 - Unused): free memory 469762048 448 shared pool (1): free memory 207961376 198.33 shared pool (2): free memory 224686568 214.28 shared pool (3): free memory 270474992 257.95 shared pool (4): free memory 234357448 223.5 shared pool (5): free memory 206367112 196.81 shared pool (6): free memory 239940912 228.83 7 rows selected. SYS@xxxx> select * from x$kghlu; SUB SSUB FLUSHED LRU LIST RECURRENT TRANSIENT RESERVED RESERVED RESERVED RESERVED FREE UNPIN LAST FRUNP ADDR INDX INST_ID POOL POOL KGHLUSHRPOOL CHUNKS OPERATIONS CHUNKS CHUNKS KGHLUMXA KGHLUMES KGHLUMER SCANS MISSES MISS SIZE MISS MAX SZ UNSUCCESS UNSUCC SIZE ---------------- ---------- ---------- ---------- ---------- ------------ ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ----------- ---------- ----------- 00007F78519F2E48 0 1 6 0 1 0 17 0 17 2147483647 0 0 0 0 0 0 0 0 00007F78519F27F8 1 1 5 0 1 0 27 0 17 2147483647 0 0 0 0 0 0 0 0 00007F78519F3E60 2 1 4 0 1 0 23 0 19 2147483647 0 0 0 0 0 0 0 0 00007F78519F3810 3 1 3 0 1 0 40 0 16 2147483647 0 0 0 0 0 0 0 0 00007F78519F4EE0 4 1 2 0 1 0 34 0 22 2147483647 0 0 0 0 0 0 0 0 00007F78519F4890 5 1 1 0 1 0 26 0 16 2147483647 0 0 0 0 0 0 0 0 6 rows selected. --// 看不出子子池的分配情况. SYS@xxxx> alter session set events 'immediate trace name heapdump level 2'; Session altered. $ egrep "sga heap|Total heap size" /u01/app/oracle/diag/rdbms/xxxx/xxxx/trace/xxxx_ora_44083.trc HEAP DUMP heap name="sga heap" desc=0x60001190 HEAP DUMP heap name="sga heap(1,0)" desc=0x6005c318 Total heap size = 67108776 HEAP DUMP heap name="sga heap(1,1)" desc=0x6005db70 Total heap size = 67108776 HEAP DUMP heap name="sga heap(1,2)" desc=0x6005f3c8 Total heap size = 67108776 HEAP DUMP heap name="sga heap(1,3)" desc=0x60060c20 Total heap size = 67108776 --// 67108776*4/1024/1024 = 255.99966430664062500000 ,接近256M. HEAP DUMP heap name="sga heap(2,0)" desc=0x60065be0 Total heap size =134217552 HEAP DUMP heap name="sga heap(2,1)" desc=0x60067438 Total heap size = 67108776 HEAP DUMP heap name="sga heap(2,2)" desc=0x60068c90 Total heap size = 67108776 HEAP DUMP heap name="sga heap(2,3)" desc=0x6006a4e8 Total heap size = 67108776 --//(134217552+67108776+67108776+67108776)/1024/1024 = 319.99958038330078125000,接近320M. HEAP DUMP heap name="sga heap(3,0)" desc=0x6006f4a8 Total heap size =134217552 HEAP DUMP heap name="sga heap(3,1)" desc=0x60070d00 Total heap size = 67108776 HEAP DUMP heap name="sga heap(3,2)" desc=0x60072558 Total heap size = 67108776 HEAP DUMP heap name="sga heap(3,3)" desc=0x60073db0 Total heap size = 67108776 HEAP DUMP heap name="sga heap(4,0)" desc=0x60078d70 Total heap size =134217552 HEAP DUMP heap name="sga heap(4,1)" desc=0x6007a5c8 Total heap size = 67108776 HEAP DUMP heap name="sga heap(4,2)" desc=0x6007be20 Total heap size = 67108776 HEAP DUMP heap name="sga heap(4,3)" desc=0x6007d678 Total heap size = 67108776 HEAP DUMP heap name="sga heap(5,0)" desc=0x60082638 Total heap size = 67108776 HEAP DUMP heap name="sga heap(5,1)" desc=0x60083e90 Total heap size = 67108776 HEAP DUMP heap name="sga heap(5,2)" desc=0x600856e8 Total heap size = 67108776 HEAP DUMP heap name="sga heap(5,3)" desc=0x60086f40 Total heap size = 67108776 HEAP DUMP heap name="sga heap(6,0)" desc=0x6008bf00 Total heap size =134217552 HEAP DUMP heap name="sga heap(6,1)" desc=0x6008d758 Total heap size = 67108776 HEAP DUMP heap name="sga heap(6,2)" desc=0x6008efb0 Total heap size = 67108776 HEAP DUMP heap name="sga heap(6,3)" desc=0x60090808 Total heap size = 67108776 --//这样可以看到每个子池有几个子子池,并且每个的大小. 总结: --//总之注意,如果手工管理内存,设置sga_target=0G的情况下,适当设置_kghdsidx_count,shared_pool_size,db_cache_size值.避免 --//shared pool latch仅仅1个的情况. --//我个性喜欢手工管理内存设置sga_target=sga_max_size,设置shared_pool_size,db_cache_size基本不会转换. --//附上sgastatx.sql脚本. $ cat sgastatx.sql -------------------------------------------------------------------------------- -- -- File name: sgastatx -- Purpose: Show shared pool stats by sub-pool from X$KSMSS -- -- Author: Tanel Poder -- Copyright: (c) http://www.tanelpoder.com -- -- Usage: @sgastatx <statistic name> -- @sgastatx "free memory" -- @sgastatx cursor -- -- Other: The other script for querying V$SGASTAT is called sgastat.sql -- -- -- -------------------------------------------------------------------------------- COL sgastatx_subpool HEAD SUBPOOL FOR a30 PROMPT PROMPT -- All allocations: SELECT 'shared pool ('||NVL(DECODE(TO_CHAR(ksmdsidx),'0','0 - Unused',ksmdsidx), 'Total')||'):' sgastatx_subpool , SUM(ksmsslen) bytes , ROUND(SUM(ksmsslen)/1048576,2) MB FROM x$ksmss WHERE ksmsslen > 0 --AND ksmdsidx > 0 GROUP BY ROLLUP ( ksmdsidx ) ORDER BY sgastatx_subpool ASC / BREAK ON sgastatx_subpool SKIP 1 PROMPT -- Allocations matching "&1": SELECT subpool sgastatx_subpool , name , SUM(bytes) , ROUND(SUM(bytes)/1048576,2) MB FROM ( SELECT 'shared pool ('||DECODE(TO_CHAR(ksmdsidx),'0','0 - Unused',ksmdsidx)||'):' subpool , ksmssnam name , ksmsslen bytes FROM x$ksmss WHERE ksmsslen > 0 AND LOWER(ksmssnam) LIKE LOWER('%&1%') ) GROUP BY subpool , name ORDER BY subpool ASC , SUM(bytes) DESC / BREAK ON sgastatx_subpool DUP [20190507]sga_target 的设置和ORA-04031错误2.txt [20190507]sga_target=0注意修改_kghdsidx_count设置.txt --//昨天遇到一例视图定义太复杂导致长时间分析sql语句出现library cache lock等待事件的情况. --//加上大量使用非绑定变量语句,导致硬解析增加,导致问题更加严重. --//顺便解析当时同事发现仅仅1个CPU特别忙.实际上因为仅仅1个shared pool latch在工作. 1.环境: > @ ver1 PORT_STRING VERSION BANNER ------------------ -------------- ---------------------------------------------------------------- IBMPC/WIN_NT-8.1.0 10.2.0.3.0 Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - Prod --//注32位版本. 2.解析: SELECT addr ,latch# ,child# ,level# ,name ,gets ,sleeps ,immediate_gets ,immediate_misses ,spin_gets FROM V$LATCH_CHILDREN WHERE name LIKE 'shared pool' ORDER BY addr; ADDR LATCH# CHILD# LEVEL# NAME GETS SLEEPS IMMEDIATE_GETS IMMEDIATE_MISSES SPIN_GETS -------- ---------- ---------- ---------- ----------- ---------- ---------- -------------- ---------------- ---------- 05AA3858 213 1 7 shared pool 25235287 182 0 0 7384 05AA38C0 213 2 7 shared pool 151 0 0 0 0 05AA3928 213 3 7 shared pool 151 0 0 0 0 05AA3990 213 4 7 shared pool 151 0 0 0 0 05AA39F8 213 5 7 shared pool 151 0 0 0 0 05AA3A60 213 6 7 shared pool 151 0 0 0 0 05AA3AC8 213 7 7 shared pool 151 0 0 0 0 7 rows selected. --//仅仅1个shared pool latch在使用. > show parameter sga_ NAME TYPE VALUE ------------- ----------- ------ sga_max_size big integer 1200M sga_target big integer 1200M > @　hide _kghdsidx_count NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE --------------- ------------------ ---------------------- ---------------------- ---------------------- _kghdsidx_count max kghdsidx count TRUE 1 1 > @ hide _enable_shared_pool_durations NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE ----------------------------- -------------------------------------- ------------- ------------- ------------ _enable_shared_pool_durations temporary to disable/enable kgh policy TRUE TRUE TRUE > show parameter cpu_count NAME TYPE VALUE --------- ------- ------ cpu_count integer 16 --//注:在任务管理器看到32个CPU.不过我发现图中下面一排16个cpu好像没有负载. --//主要问题是参数_kghdsidx_count=1.仅仅1个subpool.看来这个版本按照每个子缓冲池至少为512MB设计的. --//参数_kghdsidx_count大小由CPU数量以及共享池大小决定的.最大不过7个. --//我仅仅知道的原则: --//共享子缓冲池的分配的算法很简单： --//·每个子缓冲池必须满足一定的内存约束； --//·每4颗CPU可以分配一个子缓冲池，最多7个。 --//本来oracle这样做为了减少shared pool,但是带来另外的问题,如果每个子池太小,反而出现ora-04031错误.于是oracle限制每个子池 --//的大小,你可以发现一些blog提到减少参数_kghdsidx_count大小,限制每个子池避免出现子池太小的情况. --//在Oracle 9i中，每个SubPool至少128MB，在Oracle 10g中，每个子缓冲池至少为256MB,在Oracle 11g中，每个子缓冲池至少为512MB. --//Oracle 10g会将单个缓冲池分割再细分4个子分区进行管理(这可能是因为通常4颗CPU才分配一个SubPool), --//分别是"instance", "session", "cursor", and "execution". --//对方安装32位系统,不能设置很大sga,受限共享内存大小600M上下,这样仅仅1个shared pool latch. --//这样在大量硬解析的情况下,特别在分析sql语句很长时间的情况下仅仅1个shared pool latch自然很忙. --//也就是同事看到的情况,仅仅1个CPU在忙...而且sql语句中的视图关联的表太多,导致1条sql语句消耗共享池很大,我执行前面的语句,查看 --//v$sqlarea的SHARABLE_MEM达到512K.这样大量非绑定变量语句导致许多对象退出又再进入共享池. --//这就好比一个宾馆的前台仅仅1名接待人员一样,客户入住登记少没有问题,一旦大量客户登记入住,1个人自然忙不过来, --//而其他人根本插不上手.有时候非常像现实工作的场景,1个忙的要死,别人根本插不上手,只能在那干等^_^. 3.突然想起我以前1个测试: --//[20190104]sga_target 的设置和ORA-04031错误.txt => http://blog.itpub.net/267265/viewspace-2305567/ --//发现一个问题,就是设置sga_target=0,如果大量语句不使用绑定变量可能存在问题.参数_kghdsidx_count=1,仅仅1个shared pool latch. --//这样情况应该适当增加_kghdsidx_count,通过测试说明问题: $ export ORACLE_SID=xxxx $ cat initxxxx.ora db_name=xxxx instance_name=xxxx sga_target=0 sga_max_size=20G --//设置sga_target=0. SYS@xxxx> startup nomount ORACLE instance started. Total System Global Area 2.1379E+10 bytes Fixed Size 2262656 bytes Variable Size 2.1206E+10 bytes Database Buffers 134217728 bytes Redo Buffers 36073472 bytes SELECT addr ,latch# ,child# ,level# ,name ,gets ,sleeps ,immediate_gets ,immediate_misses ,spin_gets FROM V$LATCH_CHILDREN WHERE name LIKE 'shared pool' ORDER BY addr; ADDR LATCH# CHILD# LEVEL# NAME GETS SLEEPS IMMEDIATE_GETS IMMEDIATE_MISSES SPIN_GETS ---------------- ---------- ---------- ---------- ----------- ---- ---------- -------------- ---------------- ---------- 000000006010F288 336 1 7 shared pool 1397 0 0 0 5 000000006010F328 336 2 7 shared pool 0 0 0 0 0 000000006010F3C8 336 3 7 shared pool 0 0 0 0 0 000000006010F468 336 4 7 shared pool 0 0 0 0 0 000000006010F508 336 5 7 shared pool 0 0 0 0 0 000000006010F5A8 336 6 7 shared pool 0 0 0 0 0 000000006010F648 336 7 7 shared pool 0 0 0 0 0 7 rows selected. SYS@xxxx> @ hide _kghdsidx_count old 10: and lower(a.ksppinm) like lower('%&1%') new 10: and lower(a.ksppinm) like lower('%_kghdsidx_count%') NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE --------------- ------------------ ------------- ------------- ------------ _kghdsidx_count max kghdsidx count TRUE 1 1 SYS@xxxx> @ hide _enable_shared_pool_durations old 10: and lower(a.ksppinm) like lower('%&1%') new 10: and lower(a.ksppinm) like lower('%_enable_shared_pool_durations%') NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE ----------------------------- -------------------------------------- ------------- ------------- ------------ _enable_shared_pool_durations temporary to disable/enable kgh policy TRUE FALSE FALSE --//注意_enable_shared_pool_durations参数,在sga_target=0的情况下,_enable_shared_pool_durations的缺省值等于FALSE(实际上设 --//置为true也无效,看后面测试) --//也就是仅仅1个subpool,下面仅仅一个子子池. SYS@xxxx> @ sgastatx.sql 'free memory' -- All allocations: SUBPOOL BYTES MB ------------------------------ ---------- ---------- shared pool (0 - Unused): 67108864 64 shared pool (1): 268435456 256 shared pool (Total): 335544320 320 -- Allocations matching "free memory": old 15: AND LOWER(ksmssnam) LIKE LOWER('%&1%') new 15: AND LOWER(ksmssnam) LIKE LOWER('%free memory%') SUBPOOL NAME SUM(BYTES) MB ------------------------------ -------------------- ---------- ---------- shared pool (0 - Unused): free memory 67108864 64 shared pool (1): free memory 30813880 29.39 --//仅仅1个子池.共享内存不足的情况下会从shared pool (0 - Unused)分过来. --//另外注意1个问题,有一些文章提示查询x$kghlu可以查询这些子缓冲池的分配,我的测试不行,当然我现在sga_target=0的情况下不存 --//在子子池的情况. --//通过一个内部表X$KGHLU([K]ernel [G]eneric memory [H]eap manager State of [L]R[U] Of Unpinned Recreatable chunks)可以 --//查询这些子缓冲池的分配： (我的测试不行!!) SYS@xxxx> select * from x$kghlu; ADDR INDX INST_ID KGHLUIDX KGHLUDUR KGHLUSHRPOOL KGHLUFSH KGHLUOPS KGHLURCR KGHLUTRN KGHLUMXA KGHLUMES KGHLUMER KGHLURCN KGHLURMI KGHLURMZ KGHLURMX KGHLUNFU KGHLUNFS ---------------- ---------- ---------- ---------- ---------- ------------ ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- 00007F6D32E5EFF0 0 1 1 0 1 0 64 3 43 2147483647 0 0 0 0 0 0 0 0 --//只能通过heapdump转储获取这方面信息. SYS@xxxx> alter session set events 'immediate trace name heapdump level 2'; Session altered. $ grep 'sga heap' /u01/app/oracle/diag/rdbms/xxxx/xxxx/trace/xxxx_ora_43866.trc HEAP DUMP heap name="sga heap" desc=0x60001190 HEAP DUMP heap name="sga heap(1,0)" desc=0x6005c318 --//可以看出问题.仅仅1个子池,不细分子子池.也就是在sga_target=0的情况下,可能需要手工设置_kghdsidx_count的大小. --//不然可能出现shared pool latch的争用,特别在应用没有绑定变量的情况下. --//我个人建议sga_target=0的情况下手工设置shared_pool_size,db_cache_size. --//或者sga_target<>0的情况下,也设置shared_pool_size,db_cache_size作为最小值,避免内存在这些组件中变换. --//修改*._kghdsidx_count=3 $ cat initxxxx.ora db_name=xxxx instance_name=xxxx #sga_target=20G sga_target=0 sga_max_size=20G #pre_page_sga=true *._kghdsidx_count=3 SYS@xxxx> startup nomount ORA-04031: unable to allocate 320032 bytes of shared memory ("shared pool","unknown object","KGSK scheduler","KGSK chg class latches") --//shared_pool_size太小.仅仅320M. --//测试增加*._kghdsidx_count=3,*.shared_pool_size=1600M,*._enable_shared_pool_durations=true的情况: $ cat initxxxx.ora db_name=xxxx instance_name=xxxx sga_target=0G #sga_target=20G sga_max_size=20G #pre_page_sga=true *._kghdsidx_count=3 *.shared_pool_size=1600M *._enable_shared_pool_durations=true ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SYS@xxxx> startup nomount ORACLE instance started. Total System Global Area 2.1379E+10 bytes Fixed Size 2262656 bytes Variable Size 2.1206E+10 bytes Database Buffers 134217728 bytes Redo Buffers 36073472 by SYS@xxxx> @ hide _kghdsidx_count old 10: and lower(a.ksppinm) like lower('%&1%') new 10: and lower(a.ksppinm) like lower('%_kghdsidx_count%') NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE --------------- ------------------ ------------- ------------- ------------ _kghdsidx_count max kghdsidx count FALSE 3 3 SYS@xxxx> @ hide _enable_shared_pool_durations old 10: and lower(a.ksppinm) like lower('%&1%') new 10: and lower(a.ksppinm) like lower('%_enable_shared_pool_durations%') NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE ---------------------------------------- -------------------------------------- ------------- ------------- ------------ _enable_shared_pool_durations temporary to disable/enable kgh policy FALSE TRUE TRUE SYS@xxxx> select * from x$kghlu; ADDR INDX INST_ID KGHLUIDX KGHLUDUR KGHLUSHRPOOL KGHLUFSH KGHLUOPS KGHLURCR KGHLUTRN KGHLUMXA KGHLUMES KGHLUMER KGHLURCN KGHLURMI KGHLURMZ KGHLURMX KGHLUNFU KGHLUNFS ---------------- ---------- ---------- ---------- ---------- ------------ ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- 00007FC432A52F70 0 1 3 0 1 0 20 0 14 2147483647 0 0 0 0 0 0 0 0 00007FC432A54640 1 1 2 0 1 0 9 0 7 2147483647 0 0 0 0 0 0 0 0 00007FC432A53FF0 2 1 1 0 1 0 14 0 10 2147483647 0 0 0 0 0 0 0 0 --//仅仅3个子池.看不出子子池. SYS@xxxx> alter session set events 'immediate trace name heapdump level 2'; Session altered. $ grep 'sga heap' /u01/app/oracle/diag/rdbms/xxxx/xxxx/trace/xxxx_ora_43949.trc HEAP DUMP heap name="sga heap" desc=0x60001190 HEAP DUMP heap name="sga heap(1,0)" desc=0x6005c318 HEAP DUMP heap name="sga heap(2,0)" desc=0x60065be0 HEAP DUMP heap name="sga heap(3,0)" desc=0x6006f4a8 --//可以发现设置即使_enable_shared_pool_durations=TRUE,在sga_target=0G的情况下也不会出现子子池的情况. SYS@xxxx> @ sgastatx.sql 'free memory' -- All allocations: SUBPOOL BYTES MB ------------------------------ ---------- ---------- shared pool (0 - Unused): 1275068416 1216 shared pool (1): 134217728 128 shared pool (2): 134217728 128 shared pool (3): 134217728 128 shared pool (Total): 1677721600 1600 -- Allocations matching "free memory": old 15: AND LOWER(ksmssnam) LIKE LOWER('%&1%') new 15: AND LOWER(ksmssnam) LIKE LOWER('%free memory%') SUBPOOL NAME SUM(BYTES) MB ------------------------------ ---------------------------------------- ---------- ---------- shared pool (0 - Unused): free memory 1275068416 1216 shared pool (1): free memory 48797608 46.54 shared pool (2): free memory 34835672 33.22 shared pool (3): free memory 48306064 46.07 SELECT addr ,latch# ,child# ,level# ,name ,gets ,sleeps ,immediate_gets ,immediate_misses ,spin_gets FROM V$LATCH_CHILDREN WHERE name LIKE 'shared pool' ORDER BY addr; ADDR LATCH# CHILD# LEVEL# NAME GETS SLEEPS IMMEDIATE_GETS IMMEDIATE_MISSES SPIN_GETS ---------------- ---------- ---------- ---------- ----------- ---- ---------- -------------- ---------------- ---------- 000000006010F288 336 1 7 shared pool 732 0 1 0 0 000000006010F328 336 2 7 shared pool 673 0 1 0 0 000000006010F3C8 336 3 7 shared pool 903 0 1 0 1 000000006010F468 336 4 7 shared pool 1 0 0 0 0 000000006010F508 336 5 7 shared pool 1 0 0 0 0 000000006010F5A8 336 6 7 shared pool 1 0 0 0 0 000000006010F648 336 7 7 shared pool 1 0 0 0 0 7 rows selected. --//总之,如果手工管理内存,设置sga_target=0G的情况下,适当设置_kghdsidx_count,shared_pool_size,db_cache_size值. 4.最后测试sga_target<>0的情况: $ grep -v "^#" initxxxx.ora db_name=xxxx instance_name=xxxx sga_target=20G sga_max_size=20G SYS@xxxx> @ hide _kghdsidx_count old 10: and lower(a.ksppinm) like lower('%&1%') new 10: and lower(a.ksppinm) like lower('%_kghdsidx_count%') NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE ---------------------------------------- --------------------------------------- ------------- ------------- ------------ _kghdsidx_count max kghdsidx count TRUE 6 6 SYS@xxxx> @ hide _enable_shared_pool_durations old 10: and lower(a.ksppinm) like lower('%&1%') new 10: and lower(a.ksppinm) like lower('%_enable_shared_pool_durations%') NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE ---------------------------------------- --------------------------------------- ------------- ------------- ------------ _enable_shared_pool_durations temporary to disable/enable kgh policy TRUE TRUE TRUE SYS@xxxx> @ sgastatx.sql 'free memory' -- All allocations: SUBPOOL BYTES MB ------------------------------ ---------- ---------- shared pool (0 - Unused): 469762048 448 shared pool (1): 268435456 256 shared pool (2): 335544320 320 shared pool (3): 335544320 320 shared pool (4): 335544320 320 shared pool (5): 268435456 256 shared pool (6): 335544320 320 shared pool (Total): 2348810240 2240 8 rows selected. -- Allocations matching "free memory": old 15: AND LOWER(ksmssnam) LIKE LOWER('%&1%') new 15: AND LOWER(ksmssnam) LIKE LOWER('%free memory%') SUBPOOL NAME SUM(BYTES) MB ------------------------------ -------------------- ---------- ---------- shared pool (0 - Unused): free memory 469762048 448 shared pool (1): free memory 207961376 198.33 shared pool (2): free memory 224686568 214.28 shared pool (3): free memory 270474992 257.95 shared pool (4): free memory 234357448 223.5 shared pool (5): free memory 206367112 196.81 shared pool (6): free memory 239940912 228.83 7 rows selected. SYS@xxxx> select * from x$kghlu; SUB SSUB FLUSHED LRU LIST RECURRENT TRANSIENT RESERVED RESERVED RESERVED RESERVED FREE UNPIN LAST FRUNP ADDR INDX INST_ID POOL POOL KGHLUSHRPOOL CHUNKS OPERATIONS CHUNKS CHUNKS KGHLUMXA KGHLUMES KGHLUMER SCANS MISSES MISS SIZE MISS MAX SZ UNSUCCESS UNSUCC SIZE ---------------- ---------- ---------- ---------- ---------- ------------ ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ----------- ---------- ----------- 00007F78519F2E48 0 1 6 0 1 0 17 0 17 2147483647 0 0 0 0 0 0 0 0 00007F78519F27F8 1 1 5 0 1 0 27 0 17 2147483647 0 0 0 0 0 0 0 0 00007F78519F3E60 2 1 4 0 1 0 23 0 19 2147483647 0 0 0 0 0 0 0 0 00007F78519F3810 3 1 3 0 1 0 40 0 16 2147483647 0 0 0 0 0 0 0 0 00007F78519F4EE0 4 1 2 0 1 0 34 0 22 2147483647 0 0 0 0 0 0 0 0 00007F78519F4890 5 1 1 0 1 0 26 0 16 2147483647 0 0 0 0 0 0 0 0 6 rows selected. --// 看不出子子池的分配情况. SYS@xxxx> alter session set events 'immediate trace name heapdump level 2'; Session altered. $ egrep "sga heap|Total heap size" /u01/app/oracle/diag/rdbms/xxxx/xxxx/trace/xxxx_ora_44083.trc HEAP DUMP heap name="sga heap" desc=0x60001190 HEAP DUMP heap name="sga heap(1,0)" desc=0x6005c318 Total heap size = 67108776 HEAP DUMP heap name="sga heap(1,1)" desc=0x6005db70 Total heap size = 67108776 HEAP DUMP heap name="sga heap(1,2)" desc=0x6005f3c8 Total heap size = 67108776 HEAP DUMP heap name="sga heap(1,3)" desc=0x60060c20 Total heap size = 67108776 --// 67108776*4/1024/1024 = 255.99966430664062500000 ,接近256M. HEAP DUMP heap name="sga heap(2,0)" desc=0x60065be0 Total heap size =134217552 HEAP DUMP heap name="sga heap(2,1)" desc=0x60067438 Total heap size = 67108776 HEAP DUMP heap name="sga heap(2,2)" desc=0x60068c90 Total heap size = 67108776 HEAP DUMP heap name="sga heap(2,3)" desc=0x6006a4e8 Total heap size = 67108776 --//(134217552+67108776+67108776+67108776)/1024/1024 = 319.99958038330078125000,接近320M. HEAP DUMP heap name="sga heap(3,0)" desc=0x6006f4a8 Total heap size =134217552 HEAP DUMP heap name="sga heap(3,1)" desc=0x60070d00 Total heap size = 67108776 HEAP DUMP heap name="sga heap(3,2)" desc=0x60072558 Total heap size = 67108776 HEAP DUMP heap name="sga heap(3,3)" desc=0x60073db0 Total heap size = 67108776 HEAP DUMP heap name="sga heap(4,0)" desc=0x60078d70 Total heap size =134217552 HEAP DUMP heap name="sga heap(4,1)" desc=0x6007a5c8 Total heap size = 67108776 HEAP DUMP heap name="sga heap(4,2)" desc=0x6007be20 Total heap size = 67108776 HEAP DUMP heap name="sga heap(4,3)" desc=0x6007d678 Total heap size = 67108776 HEAP DUMP heap name="sga heap(5,0)" desc=0x60082638 Total heap size = 67108776 HEAP DUMP heap name="sga heap(5,1)" desc=0x60083e90 Total heap size = 67108776 HEAP DUMP heap name="sga heap(5,2)" desc=0x600856e8 Total heap size = 67108776 HEAP DUMP heap name="sga heap(5,3)" desc=0x60086f40 Total heap size = 67108776 HEAP DUMP heap name="sga heap(6,0)" desc=0x6008bf00 Total heap size =134217552 HEAP DUMP heap name="sga heap(6,1)" desc=0x6008d758 Total heap size = 67108776 HEAP DUMP heap name="sga heap(6,2)" desc=0x6008efb0 Total heap size = 67108776 HEAP DUMP heap name="sga heap(6,3)" desc=0x60090808 Total heap size = 67108776 --//这样可以看到每个子池有几个子子池,并且每个的大小. 总结: --//总之注意,如果手工管理内存,设置sga_target=0G的情况下,适当设置_kghdsidx_count,shared_pool_size,db_cache_size值.避免 --//shared pool latch仅仅1个的情况. --//我个性喜欢手工管理内存设置sga_target=sga_max_size,设置shared_pool_size,db_cache_size基本不会转换. --//附上sgastatx.sql脚本. $ cat sgastatx.sql -------------------------------------------------------------------------------- -- -- File name: sgastatx -- Purpose: Show shared pool stats by sub-pool from X$KSMSS -- -- Author: Tanel Poder -- Copyright: (c) http://www.tanelpoder.com -- -- Usage: @sgastatx <statistic name> -- @sgastatx "free memory" -- @sgastatx cursor -- -- Other: The other script for querying V$SGASTAT is called sgastat.sql -- -- -- -------------------------------------------------------------------------------- COL sgastatx_subpool HEAD SUBPOOL FOR a30 PROMPT PROMPT -- All allocations: SELECT 'shared pool ('||NVL(DECODE(TO_CHAR(ksmdsidx),'0','0 - Unused',ksmdsidx), 'Total')||'):' sgastatx_subpool , SUM(ksmsslen) bytes , ROUND(SUM(ksmsslen)/1048576,2) MB FROM x$ksmss WHERE ksmsslen > 0 --AND ksmdsidx > 0 GROUP BY ROLLUP ( ksmdsidx ) ORDER BY sgastatx_subpool ASC / BREAK ON sgastatx_subpool SKIP 1 PROMPT -- Allocations matching "&1": SELECT subpool sgastatx_subpool , name , SUM(bytes) , ROUND(SUM(bytes)/1048576,2) MB FROM ( SELECT 'shared pool ('||DECODE(TO_CHAR(ksmdsidx),'0','0 - Unused',ksmdsidx)||'):' subpool , ksmssnam name , ksmsslen bytes FROM x$ksmss WHERE ksmsslen > 0 AND LOWER(ksmssnam) LIKE LOWER('%&1%') ) GROUP BY subpool , name ORDER BY subpool ASC , SUM(bytes) DESC / BREAK ON sgastatx_subpool DUP

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[20190507]sga_target=0注意修改_kghdsidx_count设置.txt

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