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关于shared pool的深入探讨(三)

2017-02-04 00:00 543 查看
基本命令：

ALTER SESSION SET EVENTS 'immediate trace name LIBRARY_CACHE level LL';

其中LL代表Level级别,对于9.2.0及以后版本,不同Level含义如下:
Level =1 ,转储Library cache统计信息
Level =2 ,转储hash table概要
Level =4 ,转储Library cache对象，只包含基本信息
Level =8 ,转储Library cache对象，包含详细信息(包括child references,pin waiters等)
Level =16,增加heap sizes信息
Level =32,增加heap信息

Library cache由一个hash表组成,而hash表是一个由hash buckets组成的数组.

每个hash bucket都是包含library cache handle的一个双向链表。
Library Cache Handle指向Library Cache Object和一个引用列表.
library cache对象进一步分为:依赖表、子表和授权表等

我们看一下library cache的结构:

通过
ALTER SESSION SET EVENTS 'immediate trace name LIBRARY_CACHE level 4'
获得以下输出(这部分信息来自Oracle8i)

点击这里下载: hsbi_ora_4614.trc

第一部分(等价于Level 1):

LIBRARY CACHE STATISTICS:
gets hit ratio       pins hit ratio    reloads   invalids namespace
---------- --------- ---------- --------- ---------- ---------- ---------
619658171 0.9999160 2193292112 0.9999511       9404        380 CRSR
79698558 0.9998832  424614847 0.9999108      13589          0 TABL/PRCD/TYPE
163399 0.9979926     163402 0.9978948         16          0 BODY/TYBD
0 0.0000000          0 0.0000000          0          0 TRGR
34 0.0294118         35 0.0571429          0          0 INDX
18948 0.9968862      24488 0.9953855          0          0 CLST
0 0.0000000          0 0.0000000          0          0 OBJE
0 0.0000000          0 0.0000000          0          0 PIPE
0 0.0000000          0 0.0000000          0          0 LOB
0 0.0000000          0 0.0000000          0          0 DIR
0 0.0000000          0 0.0000000          0          0 QUEU
0 0.0000000          0 0.0000000          0          0 OBJG
0 0.0000000          0 0.0000000          0          0 PROP
0 0.0000000          0 0.0000000          0          0 JVSC
0 0.0000000          0 0.0000000          0          0 JVRE
0 0.0000000          0 0.0000000          0          0 ROBJ
0 0.0000000          0 0.0000000          0          0 REIP
0 0.0000000          0 0.0000000          0          0 CPOB
115071 0.9992179     115071 0.9930999        704          0 EVNT
0 0.0000000          0 0.0000000          0          0 SUMM
0 0.0000000          0 0.0000000          0          0 DIMN
0 0.0000000          0 0.0000000          0          0 CTX
0 0.0000000          0 0.0000000          0          0 OUTL
0 0.0000000          0 0.0000000          0          0 RULS
0 0.0000000          0 0.0000000          0          0 RMGR
0 0.0000000          0 0.0000000          0          0 UNUSED
0 0.0000000          0 0.0000000          0          0 PPLN
0 0.0000000          0 0.0000000          0          0 PCLS
0 0.0000000          0 0.0000000          0          0 SUBS
0 0.0000000          0 0.0000000          0          0 LOCS
0 0.0000000          0 0.0000000          0          0 RMOB
0 0.0000000          0 0.0000000          0          0 RSMD
699654181 0.9999117 2618209955 0.9999440      23713        380 CUMULATIVE

这部分信息也就是v$librarycache中显示的.

第二部分(等价于Level 2中的输出):

LIBRARY CACHE HASH TABLE: size=509 count=354
BUCKET    0:
BUCKET    1:
BUCKET    2: *
BUCKET    3:
BUCKET    4:
BUCKET    5: *
BUCKET    6: *
BUCKET    7:
BUCKET    8: **
BUCKET    9: ***
BUCKET   10: *
BUCKET   11: *
BUCKET   12: ***
BUCKET   13: *
BUCKET   14: *
BUCKET   15:
BUCKET   16: *
BUCKET   17:
BUCKET   18: *
BUCKET   19:
BUCKET   20:
BUCKET   21: *
BUCKET   22:
3ff0

BUCKET   23:
BUCKET   24: *
BUCKET   25:
BUCKET   26:
BUCKET   27: ***
BUCKET   28:
BUCKET   29: **
BUCKET   30:
BUCKET   31:
BUCKET   32: ***
BUCKET   33: *
BUCKET   34:
BUCKET   35:
BUCKET   36: **
BUCKET   37:
BUCKET   38: **
BUCKET   39: *
BUCKET   40: *
BUCKET   41:
BUCKET   42:
BUCKET   43:
BUCKET   44:
BUCKET   45:
BUCKET   46: ****
BUCKET   47:
BUCKET   48:
BUCKET   49: *
BUCKET   50: *
BUCKET   51:
BUCKET   52: ***
BUCKET   53: **
BUCKET   54:
BUCKET   55: *
BUCKET   56:
BUCKET   57:
BUCKET   58:
BUCKET   59: *
BUCKET   60: **
BUCKET   61:
BUCKET   62: *
BUCKET   63:
BUCKET   64: *
BUCKET   65:
BUCKET   66:
BUCKET   67: *
BUCKET   68:
BUCKET   69: **
BUCKET   70:
BUCKET   71:
BUCKET   72: *
BUCKET   73:
BUCKET   74:
BUCKET   75: *
BUCKET   76: **
BUCKET   77:
BUCKET   78: ****
BUCKET   79:
BUCKET   80: *
BUCKET   81: *
BUCKET   82:
BUCKET   83: **
BUCKET   84: *
BUCKET   85:
BUCKET   86:
BUCKET   87:
BUCKET   88:
BUCKET   89: *
BUCKET   90: *
BUCKET   91:
BUCKET   92: *
BUCKET   93: *
BUCKET   94: *
BUCKET   95:
BUCKET   96: *
BUCKET   97:
BUCKET   98:
BUCKET   99: ***
BUCKET  100: *
BUCKET  101:
BUCKET  102: *
BUCKET  103:
BUCKET  104: *
BUCKET  105:
BUCKET  106:
BUCKET  107: ****
BUCKET  108:
BUCKET  109:
BUCKET  110:
BUCKET  111: *
BUCKET  112: **
BUCKET  113:
BUCKET  114:
BUCKET  115:
BUCKET  116: *
BUCKET  117:
BUCKET  118: *****
BUCKET  119:
BUCKET  120: *
BUCKET  121:
BUCKET  122:
BUCKET  123:
BUCKET  124:
BUCKET  125: *
BUCKET  126:
BUCKET  127:
BUCKET  128: *
BUCKET  129:
BUCKET  130: *
BUCKET  131: *
BUCKET  132:
BUCKET  133:
BUCKET  134:
BUCKET  135: *
BUCKET  136:
BUCKET  137:
BUCKET  138:
BUCKET  139: *
BUCKET  140: *
BUCKET  141: *
BUCKET  142:
BUCKET  143: *
BUCKET  144:
BUCKET  145: ***
BUCKET  146:
BUCKET  147: *
BUCKET  148:
BUCKET  149:
BUCKET  150: **
BUCKET  151:
BUCKET  152:
BUCKET  153: *
BUCKET  154:
BUCKET  155:
BUCKET  156:
BUCKET  157:
BUCKET  158:
BUCKET  159:
BUCKET  160:
BUCKET  161:
BUCKET  162:
BUCKET  163:
BUCKET  164: *
BUCKET  165: *
BUCKET  166:
BUCKET  167:
BUCKET  168:
BUCKET  169:
BUCKET  170: **
BUCKET  171:
BUCKET  172: *
BUCKET  173:
BUCKET  174:
BUCKET  175: *
BUCKET  176: *
BUCKET  177:
BUCKET  178:
BUCKET  179:
BUCKET  180:
BUCKET  181: *
BUCKET  182:
BUCKET  183:
BUCKET  184:
BUCKET  185: *
BUCKET  186:
BUCKET  187:
BUCKET  188: **
BUCKET  189:
BUCKET  190: *
BUCKET  191: *
BUCKET  192:
BUCKET  193:
BUCKET  194: *
BUCKET  195: **
BUCKET  196: *
BUCKET  197: **
BUCKET  198: ****
BUCKET  199: *
BUCKET  200: *
BUCKET  201: *
BUCKET  202: **
BUCKET  203:
BUCKET  204:
BUCKET  205: **
BUCKET  206:
BUCKET  207:
BUCKET  208: *
BUCKET  209: **
BUCKET  210:
BUCKET  211: *
BUCKET  212: *
BUCKET  213: *
BUCKET  214:
BUCKET  215:
BUCKET  216:
BUCKET  217: *
BUCKET  218: *
BUCKET  219:
BUCKET  220:
BUCKET  221: *
BUCKET  222:
BUCKET  223: *
BUCKET  224:
BUCKET  225:
BUCKET  226: *
BUCKET  227:
BUCKET  228: *
BUCKET  229: **
BUCKET  230: *
BUCKET  231:
BUCKET  232: **
BUCKET  233:
BUCKET  234: *
BUCKET  235: *
BUCKET  236:
BUCKET  237:
BUCKET  238: *
BUCKET  239:
BUCKET  240: **
BUCKET  241: **
BUCKET  242: **
BUCKET  243: ***
BUCKET  244:
BUCKET  245: *
BUCKET  246:
BUCKET  247:
BUCKET  248: **
BUCKET  249:
BUCKET  250:
BUCKET  251: **
BUCKET  252:
BUCKET  253: *
BUCKET  254: *
BUCKET  255:
BUCKET  256:
BUCKET  257: **
BUCKET  258: *
BUCKET  259:
BUCKET  260:
BUCKET  261: *
BUCKET  262: **
BUCKET  263: ***
BUCKET  264:
BUCKET  265: *
BUCKET  266:
BUCKET  267: *
BUCKET  268: *
BUCKET  269:
BUCKET  270:
BUCKET  271: **
BUCKET  272: *
BUCKET  273:
BUCKET  274: *
BUCKET  275: *
BUCKET  276: **
BUCKET  277:
BUCKET  278:
BUCKET  279:
BUCKET  280:
BUCKET  281: **
BUCKET  282: *
BUCKET  283: *
BUCKET  284: *
BUCKET  285: *
BUCKET  286:
BUCKET  287: *
BUCKET  288:
BUCKET  289:
BUCKET  290: **
BUCKET  291:
BUCKET  292: *
BUCKET  293:
BUCKET  294: *
BUCKET  295:
BUCKET  296: *
BUCKET  297:
BUCKET  298:
BUCKET  299: **
BUCKET  300: *
BUCKET  301:
BUCKET  302: *
BUCKET  303: *
BUCKET  304: **
BUCKET  305: **
BUCKET  306:
BUCKET  307:
BUCKET  308: *
BUCKET  309:
BUCKET  310:
BUCKET  311: **
BUCKET  312: *
BUCKET  313:
BUCKET  314: *
BUCKET  315:
BUCKET  316:
BUCKET  317:
BUCKET  318:
BUCKET  319: ***
BUCKET  320: *
BUCKET  321: **
BUCKET  322: **
BUCKET  323:
BUCKET  324: *
BUCKET  325:
BUCKET  326: *
BUCKET  327: *
BUCKET  328: **
BUCKET  329:
BUCKET  330: *
BUCKET  331:
BUCKET  332:
BUCKET  333: *
BUCKET  334: *
BUCKET  335: ***
BUCKET  336: *
BUCKET  337: **
BUCKET  338: *
BUCKET  339: *
BUCKET  340:
BUCKET  341: *
BUCKET  342: *
BUCKET  343: **
BUCKET  344:
BUCKET  345:
BUCKET  346:
BUCKET  347: *
BUCKET  348:
BUCKET  349: ***
BUCKET  350: *
BUCKET  351:
BUCKET  352:
BUCKET  353:
BUCKET  354: *
BUCKET  355: **
BUCKET  356:
BUCKET  357:
BUCKET  358: **
BUCKET  359: *
BUCKET  360: *
BUCKET  361: **
BUCKET  362:
BUCKET  363:
BUCKET  364: *
BUCKET  365: *
BUCKET  366: **
BUCKET  367: *
BUCKET  368:
BUCKET  369: *
BUCKET  370:
BUCKET  371: ***
BUCKET  372:
BUCKET  373: *
BUCKET  374:
BUCKET  375:
BUCKET  376: *
BUCKET  377:
BUCKET  378:
BUCKET  379:
BUCKET  380:
BUCKET  381:
BUCKET  382:
BUCKET  383: **
BUCKET  384:
BUCKET  385:
BUCKET  386:
BUCKET  387: ***
BUCKET  388: *
BUCKET  389:
BUCKET  390:
BUCKET  391:
BUCKET  392:
BUCKET  393: *
BUCKET  394: *
BUCKET  395: *
BUCKET  396:
BUCKET  397:
BUCKET  398:
BUCKET  399:
BUCKET  400: **
BUCKET  401:
BUCKET  402:
BUCKET  403:
BUCKET  404:
BUCKET  405:
BUCKET  406:
BUCKET  407: *
BUCKET  408: *
BUCKET  409: *
BUCKET  410:
BUCKET  411: *
BUCKET  412:
BUCKET  413:
BUCKET  414:
BUCKET  415:
BUCKET  416: *
BUCKET  417:
BUCKET  418: *
BUCKET  419:
BUCKET  420: **
BUCKET  421: *
BUCKET  422:
BUCKET  423: **
BUCKET  424: ***
BUCKET  425:
BUCKET  426: *
BUCKET  427: *
BUCKET  428: **
BUCKET  429:
BUCKET  430:
BUCKET  431:
BUCKET  432:
BUCKET  433: *
BUCKET  434:
BUCKET  435: **
BUCKET  436: *
BUCKET  437: *
BUCKET  438:
BUCKET  439: *
BUCKET  440:
BUCKET  441:
BUCKET  442:
BUCKET  443: *
BUCKET  444:
BUCKET  445: *
BUCKET  446:
BUCKET  447: *
BUCKET  448:
BUCKET  449: *
BUCKET  450:
BUCKET  451:
BUCKET  452: *
BUCKET  453: *
BUCKET  454: *
BUCKET  455:
BUCKET  456:
BUCKET  457:
BUCKET  458: *
BUCKET  459: **
BUCKET  460:
BUCKET  461: **
BUCKET  462: *
BUCKET  463:
BUCKET  464: *
BUCKET  465: *
BUCKET  466:
BUCKET  467:
BUCKET  468:
BUCKET  469: *
BUCKET  470: *
BUCKET  471:
BUCKET  472: **
BUCKET  473: **
BUCKET  474:
BUCKET  475:
BUCKET  476:
BUCKET  477: *
BUCKET  478:
BUCKET  479: *
BUCKET  480: *
BUCKET  481: ***
BUCKET  482: **
BUCKET  483:
BUCKET  484:
BUCKET  485: **
BUCKET  486: **
BUCKET  487:
BUCKET  488: *
BUCKET  489: *
BUCKET  490:
BUCKET  491: **
BUCKET  492: *
BUCKET  493:
BUCKET  494:
BUCKET  495: *
BUCKET  496:
BUCKET  497:
BUCKET  498:
BUCKET  499:
BUCKET  500: ***
BUCKET  501:
BUCKET  502: *
BUCKET  503: *
BUCKET  504: *
BUCKET  505:
BUCKET  506: *
BUCKET  507:
BUCKET  508:
BUCKET  509:
BUCKET  510:
BUCKET  511:

在Oracle8i中,Oracle以一个很长的LIBRARY CACHE HASH TABLE来记录Library Cache的使用情况
"*"代表该Bucket中包含的对象的个数

在以上输出中我们看到Bucket 198中包含四个对象.

我们在第三部分中可以找到bucket 198:

BUCKET 198:
LIBRARY OBJECT HANDLE: handle=2c2b4ac4
name=
SELECT a.statement_id, a.timestamp, a.remarks, a.operation, a.options,
a.object_node, a.object_owner, a.object_name, a.object_instance,
a.object_type, a.optimizer, a.search_columns, a.id, a.parent_id,
a.position, a.cost, a.cardinality, a.bytes, a.other_tag,
a.partition_start, a.partition_stop, a.partition_id, a.other,
a.distribution
, ROWID
FROM plan_table a
hash=60dd47a1 timestamp=08-27-2004 10:19:28
namespace=CRSR flags=RON/TIM/PN0/LRG/[10010001]
kkkk-dddd-llll=0000-0001-0001 lock=0 pin=0 latch=0
lwt=2c2b4adc[2c2b4adc,2c2b4adc] ltm=2c2b4ae4[2c2b4ae4,2c2b4ae4]
pwt=2c2b4af4[2c2b4af4,2c2b4af4] ptm=2c2b4b4c[2c2b4b4c,2c2b4b4c]
ref=2c2b4acc[2c2b4acc,2c2b4acc]
LIBRARY OBJECT: object=2c0b1430
type=CRSR flags=EXS[0001] pflags= [00] status=VALD load=0
CHILDREN: size=16
child#    table reference   handle
------ -------- --------- --------
0 2c0b15ec  2c0b15b4 2c2c0d50
DATA BLOCKS:
data#     heap  pointer status pins change
----- -------- -------- ------ ---- ------
0 2c362290 2c0b14b4 I/-/A     0 NONE
LIBRARY OBJECT HANDLE: handle=2c3675d4
name=SYS.DBMS_STANDARD
hash=50748ddb timestamp=NULL
namespace=BODY/TYBD flags=TIM/SML/[02000000]
kkkk-dddd-llll=0000-0011-0011 lock=0 pin=0 latch=0
lwt=2c3675ec[2c3675ec,2c3675ec] ltm=2c3675f4[2c3675f4,2c3675f4]
pwt=2c367604[2c367604,2c367604] ptm=2c36765c[2c36765c,2c36765c]
ref=2c3675dc[2c3675dc,2c3675dc]
LIBRARY OBJECT: object=2c1528e8
flags=NEX[0002] pflags= [00] status=VALD load=0
DATA BLOCKS:
data#     heap  pointer status pins change
----- -------- -------- ------ ---- ------
0 2c367564 2c1529cc I/-/A     0 NONE
4 2c15297c        0 -/P/-     0 NONE
LIBRARY OBJECT HANDLE: handle=2c347dd8
name=select pos#,intcol#,col#,spare1 from icol$ where obj#=:1
hash=fa15ebe3 timestamp=07-28-2004 18:04:43
namespace=CRSR flags=RON/TIM/PN0/SML/[12010000]
kkkk-dddd-llll=0000-0001-0001 lock=0 pin=0 latch=0
lwt=2c347df0[2c347df0,2c347df0] ltm=2c347df8[2c347df8,2c347df8]
pwt=2c347e08[2c347e08,2c347e08] ptm=2c347e60[2c347e60,2c347e60]
ref=2c347de0[2c347de0,2c347de0]
LIBRARY OBJECT: object=2c1cd1a0
type=CRSR flags=EXS[0001] pflags= [00] status=VALD load=0
CHILDREN: size=16
child#    table reference   handle
------ -------- --------- --------
0 2c1cd35c  2c1cd324 2c281678
1 2c1cd35c  2c352c50 2c0eeb8c
2 2c1cd35c  2c352c6c 2c2bb05c
DATA BLOCKS:
data#     heap  pointer status pins change
----- -------- -------- ------ ---- ------
0 2c2e8c58 2c1cd224 I/-/A     0 NONE
LIBRARY OBJECT HANDLE: handle=2c3a6484
name=SYS.TS$
hash=bb42852e timestamp=04-24-2002 00:04:15
namespace=TABL/PRCD/TYPE flags=PKP/TIM/KEP/SML/[02900000]
kkkk-dddd-llll=0111-0111-0119 lock=0 pin=0 latch=0
lwt=2c3a649c[2c3a649c,2c3a649c] ltm=2c3a64a4[2c3a64a4,2c3a64a4]
pwt=2c3a64b4[2c3a64b4,2c3a64b4] ptm=2c3a650c[2c3a650c,2c3a650c]
ref=2c3a648c[2c0d4b14,2c09353c]
LIBRARY OBJECT: object=2c3a626c
type=TABL flags=EXS/LOC[0005] pflags= [00] status=VALD load=0
DATA BLOCKS:
data#     heap  pointer status pins change
----- -------- -------- ------ ---- ------
0 2c3a8ea4 2c3a63b0 I/P/A     0 NONE
3 2c3a5828        0 -/P/-     0 NONE
4 2c3a6300 2c3a5960 I/P/A     0 NONE
8 2c3a6360 2c3a4f00 I/P/A     0 NONE

我们看到这里包含了四个对象.

我们再来看看Oracle9i中的情况:

参考文件: hsjf_ora_15800.trc

LIBRARY CACHE HASH TABLE: size=131072 count=217
Buckets with more than 20 objects:
NONE
Hash Chain Size     Number of Buckets
---------------     -----------------
0                130855
1                   217
2                     0
3                     0
4                     0
5                     0
6                     0
7                     0
8                     0
9                     0
10                     0
11                     0
12                     0
13                     0
14                     0
15                     0
16                     0
17                     0
18                     0
19                     0
20                     0
>20                     0

Oracle9i中通过新的方式记录Library Cache的使用状况.
按不同的Hash Chain Size代表Library Cache中包含不同对象的个数.
0表示Free的Bucket,>20表示包含超过20个对象的Bucket的个数.

从以上列表中我们看到,包含一个对象的Buckets有217个,包含0个对象的Buckets有130855个.

我们来验证一下:

[oracle@jumper udump]$ cat hsjf_ora_15800.trc |grep BUCKET|more
BUCKET 12:
BUCKET 12 total object count=1
BUCKET 385:
BUCKET 385 total object count=1
BUCKET 865:
BUCKET 865 total object count=1
...

[oracle@jumper udump]$ cat hsjf_ora_15800.trc |grep BUCKET|wc -l

434

[oracle@jumper udump]$

434/2 = 217，证实了我们的猜想.

通过HASH TABLE算法的改进,Oracle Library Cache管理的效率大大提高.
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