Oracle memory structure (part 3)

Oracle memory structure (part 3)

[In-depth analysis-eygle] Study Notes

1.2.3 PGA management:

sys@felix SQL>show parameter area_size NAME                                 TYPE                   VALUE------------------------------------ ----------------------------------------------------bitmap_merge_area_size               integer                1048576create_bitmap_area_size              integer                8388608hash_area_size                       integer                131072sort_area_size                       integer                65536workarea_size_policy                 string                 AUTO 

Automatic SQL Execution Memory Management, also known as automatic PGA Management, uses this new feature, oracle can automatically manage and adjust the SQL Memory zone under the overall PGA usage limit, which greatly simplifies DBA's work? High database performance.

To achieve automatic PGA management, Oracle introduces several new initialization parameters:

(1) PGA_AGGREGATE_TARGET this parameter is used to specify the maximum PGA memory available for all sessions. This parameter can be dynamically changed. The value range is from 10 MB ~ (4096G-1) bytes.

(2) WORKAREA_SIZE_POLICY this parameter is used to switch the automatic PGA memory management function. This parameter has two options: AUTO and MANUAL. When set to AUTO, the database uses the automatic PGA management function, when it is set to MANUAL, the previous MANUAL management method is still used.

By default, the parameter WORKAREA_SIZE_POLICY is set to AUTO.

sys@felix SQL>show parameterWORKAREA_SIZE_POLIC NAME                                 TYPE                   VALUE---------------------------------------------------------- --------workarea_size_policy                 string                 AUTO

In addition, in different versions, automatic PGA management has different categories:

(1) In Oracle9i,The PGA_AGGREGATE_TARGET parameter is valid only for dedicated connections of the DedicatedServer in dedicated Server mode, but not for Shared Server connections.

(2)PGA_AGGREGATE_TARGET takes effect for both dedicated server connections and shared server connections starting from Oracle10g.

1.2.4 parameter settings and Memory Allocation

The workspace performance is expected to achieve the following goals:

Workarea execution-optimal> = 90%

Workarea execution-multipass = 0%

PGA performance indicator script of the production system:

SELECT NAME,      VALUE,       100 *      (VALUE / DECODE((SELECT SUM(VALUE)                         FROM v$sysstat                        WHERE NAME LIKE'workarea executions%'),                       0,                       NULL,                       (SELECT SUM(VALUE)                          FROM v$sysstat                         WHERE NAME LIKE'workarea executions%'))) pct  FROMv$sysstat WHERE NAMELIKE 'workarea executions%';

 

<strong>sys@felix SQL>select description,dest fromx$messages where description like 'SQL Memory%'; DESCRIPTION                                        DEST-------------------------------------------------- ----------SQL Memory Management Calculation                  CKPT 15:26:04 sys@felix SQL></strong>

sys@felix SQL>select * from v$pgastat;NAME                                          VALUE UNIT---------------------------------------- ---------- ------------------------aggregate PGA target parameter            146800640 bytesaggregate PGA auto target                  22099968 bytesglobal memory bound                        29360128 bytestotal PGA inuse                           122360832 bytestotal PGA allocated                       144107520 bytesmaximum PGA allocated                     163160064 bytestotal freeable PGA memory                  11141120 bytesprocess count                                    32max processes count                              36PGA memory freed back to OS               374669312 bytestotal PGA used for auto workareas                 0 bytesmaximum PGA used for auto workareas         6313984 bytestotal PGA used for manual workareas               0 bytesmaximum PGA used for manual workareas             0 bytesover allocation count                             0bytes processed                           232915968 bytesextra bytes read/written                          0 bytescache hit percentage                            100 percentrecompute count (total)                        600419 rows selected. 

1.2.6 PGA adjustment suggestions

With the introduction of the automatic PGA adjustment function, Oracle also introduces the corresponding dynamic performance view for optimization recommendations. The PGA optimization recommendations are provided through v $ pga_target_advice and v $ pga_target_advice_histogra. The v $ pga_target_advice view evaluates different PGA settings and provides information such as the PGA hit rate and OverAlloc under different settings.

15:32:23 sys@felix SQL>select PGA_TARGET_FOR_ESTIMATE/1024/1024 PGAMB, PGA_TARGET_FACTOR, 15:37:08   2  ESTD_PGA_CACHE_HIT_PERCENTAGE, ESTD_OVERALLOC_COUNT15:37:08   3  from v$pga_target_advice;     PGAMB PGA_TARGET_FACTOR ESTD_PGA_CACHE_HIT_PERCENTAGE ESTD_OVERALLOC_COUNT---------- ----------------- ----------------------------- --------------------      17.5              .125                            85                    4        35               .25                            85                    4        70                .5                            85                    4       105               .75                            85                    4       140                 1                           100                    0       168               1.2                           100                    0       196               1.4                           100                    0       224               1.6                           100                    0       252               1.8                           100                    0       280                 2                           100                    0       420                 3                           100                    0       560                 4                           100                    0       840                 6                           100                    0      1120                 8                           100                    0

V $ pga_target_advice_histogram view can be evaluated by sampling different workspace sizes? For Statistics

For analysis. Several important fields are:

(1) minimum Optimal limit (bytes) within the LOW_OPTIMAL_SIZE-Histogram evaluation range)

(2) HIGH_OPTIMAL_SIZE-Histogram assessment range within the Optimal upper limit (bytes)

(3) Estimated number of optimal executions within the ESTD_OPTIMAL_EXECUTIONS-Histogram evaluation Interval

(4) Estimation of onepass executions within the ESTD_ONEPASS_EXECUTIONS-Histogram evaluation Interval

(5) Estimated number of multipass executions in the ESTD_MULTIPASSES_EXECUTIONS-Histogram evaluation Interval

(6) estimated total number of executions within the ESTD_TOTAL_EXECUTIONS-Histogram evaluation Interval

SELECT pga_target_factor factor,       low_optimal_size / 1024 low,       ROUND(high_optimal_size / 1024) high,       estd_optimal_executions estd_opt,       estd_onepass_executions estd_op,       estd_multipasses_executions estd_mp,       estd_total_executions estd_exec  FROM v$pga_target_advice_histogram WHERE pga_target_factor = 0.25   AND estd_total_executions > 0;

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<Span style = "font-family: Arial, Helvetica, sans-serif; "> heap name =" pga heap "desc = 0xbaf3ca0 -- note here </span> </strong> </span>

 extentsz=0x20c0 alt=216 het=32767 rec=0 flg=3 opc=2 parent=(nil)owner=(nil) nex=(nil) xsz=0xfff0 heap=(nil) fl2=0x60,nex=(nil), dsxvers=1, dsxflg=0x0 dsx firstext=0xf7fa7720EXTENT 0 addr=0x7fadf7c72010  Chunk     7fadf7c72020 sz=    65504   free      "               "EXTENT 1 addr=0x7fadf7d00010  Chunk     7fadf7d00020 sz=    28920   perm      "perm           "  alo=9384  Chunk     7fadf7d07118 sz=     7656   free      "               "  Chunk     7fadf7d08f00 sz=     4224   freeable  "diag pga       " ds=0x7fadf82157e0  Chunk     7fadf7d09f80 sz=     4224   freeable  "diag pga       " ds=0x7fadf82157e0/heap                                                                                                                              Chunk     7fadf7fd28d0 sz=     7608   perm      "perm           "  alo=7608  Chunk     7fadf7fd4688 sz=       40   free      "               "  Chunk     7fadf7fd46b0 sz=       80   freeable  "dbgdInitEventGr"  Chunk     7fadf7fd4700 sz=      184   freeable  "sdbgrf: iosb   "  Chunk     7fadf7fd47b8 sz=       80   freeable  "skgfzctx       "  Chunk     7fadf7fd4808 sz=      376   freeable  "PLS cca hpdesc"EXTENT 18 addr=0x7fadf7fcd860  Chunk     7fadf7fcd870 sz=    20512   perm      "perm           "  alo=20512EXTENT 19 addr=0x7fadf7fc9958  Chunk     7fadf7fc9968 sz=    16072   perm      "perm           "  alo=16072EXTENT 20 addr=0x7fadf7fc7868  Chunk     7fadf7fc7878 sz=     3240   perm      "perm           "  alo=3240  Chunk     7fadf7fc8520 sz=     3184   perm      "perm           "  alo=3184  Chunk     7fadf7fc9190 sz=     1088   perm      "perm           "  alo=1088  Chunk     7fadf7fc95d0 sz=      168   perm      "perm           "  alo=168  Chunk     7fadf7fc9678 sz=       48   free      "               "  Chunk     7fadf7fc96a8 sz=       72   freeable  "koh-kghu callh"  Chunk     7fadf7fc96f0 sz=      568   freeable  "joxp heap      "EXTENT 21 addr=0x7fadf7fc5778  Chunk     7fadf7fc5788 sz=     4848   perm      "perm           "  alo=4848  Chunk     7fadf7fc6a78 sz=      440   freeable  "krbabrPgaRespMs"  Chunk     7fadf7fc6c30 sz=       56   freeable  "krbabrPgaReqCtx"  Chunk     7fadf7fc6c68 sz=      424   freeable  "krbabrPgaReqMsg"  Chunk     7fadf7fc6e10 sz=     2600   freeable  "kjztprq struct"EXTENT 22 addr=0x7fadf7fc3688  Chunk     7fadf7fc3698 sz=     7720   perm      "perm           "  alo=7720  Chunk     7fadf7fc54c0 sz=      160   freeable  "regheapd_kdlwpg"  Chunk     7fadf7fc5560 sz=       88   freeable  "KCFIS GCTX     "  Chunk     7fadf7fc55b8 sz=      400   freeable  "krbabrPgaStbyRe"EXTENT 23 addr=0x7fadf7fb5e28  Chunk     7fadf7fb5e38 sz=    55328   perm      "perm           "  alo=55328EXTENT 24 addr=0x7fadf7fb3d38  Chunk     7fadf7fb3d48 sz=     4888   perm      "perm           "  alo=4888  Chunk     7fadf7fb5060 sz=     2992   recreate  "KSFQ heap      " latch=(nil) 

Further, a specific data storage structure can be dumped out (DS). For example, the size of the space used by ds dcd00c0 is sz = 14036, first, convert the space address:

select to_number('baf3ca0','xxxxxxxxxx') from dual15:50:33 sys@felix SQL>/TO_NUMBER('BAF3CA0','XXXXXXXXXX')---------------------------------                        19603369615:50:33 sys@felix SQL>

Run the following command to dump the content of a fixed address space:

Alter session set events 'immediate trace name heapdump_addr level 1, addr n ';

You can run the following command to dump the calculated address space:

SQL> ALTER SESSIONSET EVENTS 'immediate trace name heapdump_addr level 1, addr 100 ';

Session altered.

Script for getting the dump file:

SELECT a.VALUE || b.symbol || c.instance_name || '_ora_' || d.spid ||       '.trc' trace_file  FROM (SELECT VALUE FROM v$parameter WHERE NAME = 'user_dump_dest') a,       (SELECT SUBSTR(VALUE, -6, 1) symbol          FROM v$parameter         WHERE NAME = 'user_dump_dest') b,       (SELECT instance_name FROM v$instance) c,       (SELECT spid          FROM v$session s, v$process p, v$mystat m         WHERE s.paddr = p.addr           AND s.SID = m.SID           AND m.statistic# = 0) d;

Check the process dump file to find the following Heap address information and space allocation:

[oracle@felix ~]$grep heap  /u01/app/oracle/diag/rdbms/felix/felix/trace/felix_ora_6443.trc<strong><span style="color:#ff0000;">HEAP DUMP heap name="pga heap"  desc=0xbaf3ca0</span></strong> parent=(nil) owner=(nil) nex=(nil) xsz=0xfff0 heap=(nil)  Chunk     7fadf7fc96f0 sz=      568    freeable  "joxp heap      "  Chunk     7fadf7fc54c0 sz=      160    freeable  "regheapd_kdlwpg"  Chunk     7fadf7fb5060 sz=     2992    recreate  "KSFQ heap      "  latch=(nil)  Chunk     7fadf7fb5c10 sz=      160    freeable  "KSFQ heap descr"  Chunk     7fadf7fb0790 sz=      232    freeable  "iovecheapd_kdlw"  Chunk     7fadf7fb0878 sz=      304    freeable  "bcheapd_kdlwpga"  Chunk     7fadf7fb09a8 sz=      208    freeable  "sioheapd_kdlwpg"  Chunk     7fadf7fb0ad8 sz=      160    freeable  "KSZ pga subheap"Total heap size    =   499952<strong><span style="color:#ff0000;">HEAP DUMP heap name="top call heap"  desc=0xbaf94e0</span></strong> parent=(nil) owner=(nil) nex=(nil) xsz=0xfff8 heap=(nil)  Chunk     7fadf7ccb7d8 sz=     1032    recreate  "callheap       "  latch=(nil)  Chunk     7fadf7cceb78 sz=     4224    freeable  "callheap       "  ds=0xbaf85c0  Chunk     7fadf7ccfbf8 sz=     1032    recreate  "callheap       "  latch=(nil)Total heap size    =   524096

<strong><span style="color:#ff0000;">HEAP DUMP heap name="top uga heap"  desc=0xbaf9700</span></strong> parent=(nil) owner=(nil) nex=(nil) xsz=0xfff8 heap=(nil)  Chunk     7fadf7c62018 sz=    65512    freeable  "session heap   "  ds=0x7fadf7cd5be0  Chunk     7fadf7d10018 sz=    65512    freeable  "session heap   "  ds=0x7fadf7cd5be0  Chunk     7fadf7cf0018 sz=    65512    freeable  "session heap   "  ds=0x7fadf7cd5be0  Chunk     7fadf7ce0068 sz=    65432    recreate  "session heap   "  latch=(nil)Total heap size    =   262048<strong><span style="color:#ff0000;">HEAP DUMP heap name="pga heap"  desc=0xbaf3ca0</span></strong> parent=(nil) owner=(nil) nex=(nil) xsz=0x1fff0 heap=(nil)  Chunk     7fadf7fc96f0 sz=      568    freeable  "joxp heap      "  Chunk     7fadf7fc54c0 sz=      160    freeable  "regheapd_kdlwpg"  Chunk     7fadf7fb5060 sz=     2992    recreate  "KSFQ heap      "  latch=(nil)  Chunk     7fadf7fb5c10 sz=      160    freeable  "KSFQ heap descr"  Chunk     7fadf7fb0790 sz=      232    freeable  "iovecheapd_kdlw"  Chunk     7fadf7fb0878 sz=      304    freeable  "bcheapd_kdlwpga"  Chunk     7fadf7fb09a8 sz=      208    freeable  "sioheapd_kdlwpg"  Chunk     7fadf7fb0ad8 sz=      160    freeable  "KSZ pga subheap"Total heap size    =   827504

It can be seen from the red font above. In the automatic management mode, PGA, CGA, and UGA are allocated independently.