1 Julian Dyke Independent Consultant © 2005 Julian Dyke SGA Internals Web Version juliandyke.com

1

Julian Dyke

Independent Consultant

© 2005 Julian Dyke

SGAInternals

Web Version

juliandyke.com

2 © 2005 Julian Dykejuliandyke.com

Agenda Introduction SGA

Granules Fixed SGA Buffer Cache Shared Pool

Permanent Areas Heaps Subheaps Library Cache Reserved Area

Log Buffer Conclusion


Introduction Examples based on

32 bit architecture Red Hat 2.1 AS Oracle 9.2.0.4 Single (non-RAC) instance

Examples affected by Oracle version Operating system Single instance / RAC Architecture (32/64) Parameters


Word Length Word length can be

32 bit - 4 byte pointers 64 bit - 8 byte pointers

Also affects size of some integer variables e.g. int word alignment

When moving from 32 bit to 64 bit Oracle recommends doubling SHARED_POOL_SIZE SHARED_POOL_RESERVED_SIZE LARGE_POOL_SIZE


Double Linked Lists - Insertion Frequently used in SGA structures Each element includes pointers to next and previous elements Requires 8 bytes (32 bit systems) or 16 bytes (64 bit systems)

55443080 55845C54 52175AC0

HeadTail

5000F430

5000F430

5544308055443080

5000F430

55845C5455845C54 52175AC052175AC0

STOP


Double Linked Lists - Deletion Double linked lists are more efficient for

insertion deletion

55443080 55845C54

HeadTail

5000F430 52175AC0

5000F430

5544308055443080

5000F430

55845C54

55845C54 52175AC0

52175AC0

STOP


Memory Areas An Oracle process includes

the following memory areas

Executable PGA/Session Heap Shared Libraries SGA Stack

08048000

0AAA28C0

40000000

50000000

584A4000

Executable

PGASession Heap

SharedLibraries

SGA

Stack

STOP


Shared Memory Shared memory can be dumped to trace file using

ORADEBUG SETMYPIDORADEBUG IPC

$ sqlplus /nolog

SQL> CONNECT SYS/<password> AS SYSDBAConnected

SQL> ORADEBUG SETMYPIDStatement processed

SQL> ORADEBUG IPCInformation written to trace file

SQL> ORADEBUG TRACEFILE_NAME/var/opt/oracle/admin/LX092001/udump/lx092001_ora_9824.trc


Area #0 `Fixed Size' containing Subareas 0-0 Total size 000000000006e5cc Minimum Subarea size 00000000 Area Subarea Shmid Stable Addr Actual Addr 0 0 163840 0x00000050000000 0x00000050000000 Subarea size Segment size 000000000006f000 0000000008800000 Area #1 `Variable Size' containing Subareas 1-1 Total size 0000000008000000 Minimum Subarea size 00400000 Area Subarea Shmid Stable Addr Actual Addr 1 1 163840 0x0000005006f000 0x0000005006f000 Subarea size Segment size 0000000008391000 0000000008800000 Area #2 `Redo Buffers' containing Subareas 2-2 Total size 00000000000a3000 Minimum Subarea size 00000000 Area Subarea Shmid Stable Addr Actual Addr 2 2 163840 0x00000058400000 0x00000058400000 Subarea size Segment size 00000000000a3000 0000000008800000 Area #3 `skgm overhead' containing Subareas 3-3 Total size 0000000000001000 Minimum Subarea size 00000000 Area Subarea Shmid Stable Addr Actual Addr 3 3 163840 0x000000584a3000 0x000000584a3000 Subarea size Segment size 0000000000001000 0000000008800000

ORADEBUG IPC - Example Area #0 `Fixed Size' containing Subareas 0-0 Total size 000000000006e5cc Minimum Subarea size 00000000 Area Subarea Shmid Stable Addr Actual Addr 0 0 163840 0x00000050000000 0x00000050000000 Subarea size Segment size 000000000006f000 0000000008800000 Area #1 `Variable Size' containing Subareas 1-1 Total size 0000000008000000 Minimum Subarea size 00400000 Area Subarea Shmid Stable Addr Actual Addr 1 1 163840 0x0000005006f000 0x0000005006f000 Subarea size Segment size 0000000008391000 0000000008800000 Area #2 `Redo Buffers' containing Subareas 2-2 Total size 00000000000a3000 Minimum Subarea size 00000000 Area Subarea Shmid Stable Addr Actual Addr 2 2 163840 0x00000058400000 0x00000058400000 Subarea size Segment size 00000000000a3000 0000000008800000 Area #3 `skgm overhead' containing Subareas 3-3 Total size 0000000000001000 Minimum Subarea size 00000000 Area Subarea Shmid Stable Addr Actual Addr 3 3 163840 0x000000584a3000 0x000000584a3000 Subarea size Segment size 0000000000001000 0000000008800000

OS Specific

Fixed Area

Variable Area

Redo Buffers

STOP

10

© 2005 Julian Dykejuliandyke.com

V$SGA Describes sizes of main components in SGA Used by SHOW SGA command in SQL*Plus

Name Value

Fixed Size 452044

Variable Size 83886080

Database Buffers 50331648

Redo Buffers 667648

SELECT name, value FROM v$sga;

Based from X$KSMSD X$KSMSD derived from ksmstv_ (ksmst) in Fixed SGA


Shared Global Area Contains

Fixed SGA Buffer Pool Shared Pool Oracle 7.0 and above Large Pool Oracle 8.0 and above Java Pool Oracle 8.1.5 and above Streams Pool Oracle 10.1 and above Redo buffers

Buffer Pool includes Default cache Keep and Recycle cache Oracle 8.0 and above 2K, 4K, 8K, 16K and 32K cache Oracle 9.0.1 and above

12


Granules Introduced in Oracle 9.0.1

SGA divided into granules

In Oracle 9.2 granule size dependent on SGA_MAX_SIZE 4 mb SGA_MAX_SIZE <= 128 mb 16 mb SGA_MAX_SIZE > 128 mb

If SGA_MAX_SIZE not set explicitly then defaults to sum of individual pool parameters

SGA_MAX_SIZE cannot be dynamically modified

13


Granules Pool parameters rounded up to nearest granule

Each pool occupies one or more granules

Different buffer caches held in separate granules

First "granule" contains Fixed SGA Granule directory Heap headers

Last "granule" contains Guard pages Redo buffer Operating system specific overhead Remaining space unused

14


GranulesSGA_MAX_SIZE = 128M

DB_CACHE_SIZE = 48M

JAVA_POOL_SIZE = 20M

LARGE_POOL_SIZE = 12M

SHARED_POOL_SIZE = 20M

128M

4M

4M

Note – shared pool size automatically increased from 20M to 32M

Buffer Pool 48M

Free 16M

Fixed SGA 4M

Large Pool 12M

Shared Pool 32M

Java Pool 20M

Redo Buffer 4M

STOP

15


Granule Operations The following pools can be dynamically resized

Pool Parameter Version

Shared Pool SHARED_POOL_SIZE 9.0.1 and above

Default DB_CACHE_SIZE 9.0.1 and above

2K DB_2K_CACHE_SIZE 9.0.1 and above





Keep DB_KEEP_CACHE_SIZE 9.0.1 and above

Recycle DB_RECYCLE_CACHE_SIZE 9.0.1 and above

Large Pool LARGE_POOL_SIZE 9.2.0 and above

Java Pool JAVA_POOL_SIZE 10.1 and above

Streams pool cannot be dynamically resized in Oracle 10.1

16


Granule Views The following views support dynamic memory management

Introduced in Oracle 9.2 V$SGA_DYNAMIC_COMPONENTS V$SGA_DYNAMIC_FREE_MEMORY V$SGA_CURRENT_RESIZE_OPS V$SGA_RESIZE_OPS

Not always reliable

Introduced in Oracle 10.1 V$SGAINFO

17


X$KSMGEIntroduced in Oracle 9.2Describes individual granules

ADDR RAW(4)

INDX NUMBER

INST_ID NUMBER

GRANNUM NUMBER

GRANTYPE NUMBER

GRANSTATE VARCHAR2(16)

GRANFLAGS NUMBER

LOCALITY NUMBER

BASEADDR RAW(4)

GRANSIZE NUMBER

GRANNEXT NUMBER

GRANPREV NUMBER

INVALID (Free)ALLOCATED

Granule Address

Granule Size

Next granule ID

Previous granule ID

Granule ID

0 Free2 Shared Pool3 Large Pool4 Java Pool5 Buffer Pool

18


Granule Dumps Granules can be dumped using

ALTER SESSION SET EVENTS‘immediate trace name granulelist level <level>’

where <level> is

Heap Level

Null Granule 255

Home Granule 511

Shared Pool 767

Large Pool 1023

Java Pool 1279

Buffer Cache 1535

19


Fixed SGA Area containing all fixed variables Contains pointers to all other structures in SGA Variable name, type, address and size

determined when Oracle executable is linked Located at start of first granule of SGA

Fixed SGA

Granule Directory

Heap Headers

5001D9E8

5001DF50

50000000

STOP

20


X$KSMFSV Externalises name, type, address and size of all variables in

fixed SGA

ADDR RAW(4)

INDX NUMBER

INST_ID NUMBER

KSMFSNAM VARCHAR2(64)

KSMFSTYP VARCHAR2(64)

KSMFSADR RAW(4)

KSMFSSIZ NUMBER

Name

Type

Address

Size

SGA can be dumped using

ORADEBUG FIXEDSGA

21


Global Area Dumps Global areas can be dumped using

ALTER SESSION SET EVENTS‘immediate trace name global_area level <level>’

where <level> is

Heap Level

PGA 1

SGA 2

PGA + SGA 3

UGA 4

PGA + UGA 5

SGA + UGA 6

PGA + SGA + UGA 7

More detail is included at levels 0x08 0x10 0x18 (OR)

22


X$KSMMEM Externalises contents of all locations in the SGA

ADDR RAW(4)

INDX NUMBER

INST_ID NUMBER

KSMMMVAL RAW(4)Value

Address

Does not work on Windows platforms

23


Buffer Cache

Buffer Cache includes 12 x 4M granules

Each granule contains 500 buffers

Buffer Cache contains 6000 buffers

51400000

51800000

51C00000

52000000

52400000

52800000

52C00000

53000000

53400000

53800000

53C00000

54000000

DB_CACHE_SIZE = 48M DB_BLOCK_SIZE = 8192

Block Size

Buffers Per Granule

4mb 16mb

2048 1875 7503

4096 979 3916

8192 500 2002

16384 253 1012

32768 127 509STOP

24


Buffer Headers Each buffer has a buffer header In 9.2.0.4 buffer headers are 188 bytes Buffer headers are stored in same granule as buffers Buffer headers include

Replacement list Hash list Pointer to buffer

Buffer Headers

Granule

Buffers

STOP

25


X$BH Externalises buffer headers

ADDR RAW(4)

INDX NUMBER

INST_ID NUMBER

HLADDR RAW(4)

BLSIZ NUMBER

NXT_HASH RAW(4)

PRV_HASH RAW(4)

NXT_REPL RAW(4)

PRV_REPL RAW(4)

TS# NUMBER

FILE# NUMBER

DBARFIL NUMBER

DBABLK NUMBER

OBJ NUMBER

BA RAW(4)

CR_SCN_BAS NUMBER

Hash List Address

Block Size

Hash List

Replacement List

Tablespace#

Absolute File Number

Relative File Number

Block Number

Object ID

Buffer Address

26


Shared Pool56400000

56800000

56C00000

57000000

57400000

57800000

57C00000

58000000

Shared Pool includes

Permanent Area

Segmented Arrays

Library Cache

Row Cache

Reserved Area

Shared Pool occupies

8 x 4M granules = 32M

SHARED_POOL_SIZE = 20M

STOP

27


V$SGASTAT Describes sizes of individual components in SGA

Pool Name Value

fixed sga 452044

buffer cache 50331648

log buffer 656384

shared pool enqueues 51680

shared pool sessions 91656

shared pool library cache 1480240

shared pool dictionary cache 1614976

shared pool free memory 19746760

large pool free memory 12582912

java pool free memory 20971520

SELECT pool, name, value FROM v$sgastat;

28


Permanent Areas

SELECT ksmchptr, ksmchsizFROM x$ksmspWHERE ksmchcls = 'perm';

Address Size

5641F000 3967868

5681F000 2718736

56AB6C10 905116

56C1F00 4063188

5701F000 4067328

56400000

56800000

56C00000

57000000

57400000

57800000

57C00000

58000000

Allocated at instance startup Contain structures such as

processes sessions segmented arrays

STOP

29


Sessions Array of sessions stored in shared pool permanent area Allocated at instance startup Number of elements specified by SESSIONS parameter In Oracle 9.2 each element is 2412 bytes Session array externalised by

X$KSUSE General information Used by V$SESSION

X$KSUSESTA Statistics Used by V$SESSTAT

X$KSUSECST Current Waits Used by V$SESSION_WAIT

30


Sessions

X$KSUSEV$SESSION

X$KSUSECSTV$SESSION_WAIT

X$KSUSESTAV$SESSTAT

Array ofPointers

struct ksusg

ksusga_

STOP

31


Segmented Arrays Used to store arrays of objects

Array too large to fit in granule Array may grow dynamically

Objects using segmented arrays include enqueues (locks) enqueue resources (resources) transactions transaction branches

Segmented arrays managed recursively by segmented array

Segmented arrays externalised in X$KSMDD

32


Segmented Arrays

SegmentedArrays

Call

Enqueues

EnqueueResources

SegmentedArray

HeaderSegmented

Array

SegmentedArray

Header

SegmentedArray

STOP

33


X$KSMDD Externalises segmented array headers

ADDR RAW(4)

INDX NUMBER

INST_ID NUMBER

NAME VARCHAR2(30)

ELEMENTS_CHUNK NUMBER

ITEMS_PT NUMBER

INITENTRIES NUMBER

NUMENTRIES NUMBER

CURENTRIES NUMBER

NUMCHUNKS NUMBER

ELEMSIZE NUMBER

FLAGS NUMBER

HEAP RAW(4)

SECONDARY RAW(4)

Name of array

Address of parent heap

Number of chunks

34


Heaps A heap consists of one or more extents Each heap extent occupies a single granule Each extent contains one or more chunks Each heap has a header containing

list of used chunks list of free chunks

Extent 0 Extent 1 Extent 2HeapHeader

Free List Chunks

STOP

35


Chunks Chunks contain

header body

Size of chunk header dependent on chunk type 16 bytes <= size <= 32 bytes

Chunks chained through extent

Chunks can be permanent recreatable freeable free

Extent

ExtentHeader

ChunkHeader

ChunkBody

STOP

36


X$KSMSP Externalises chunks in the shared pool

ADDR RAW(4)

INDX NUMBER

INST_ID NUMBER

KSMCHIDX NUMBER

KSMCHDUR NUMBER

KSMCHCOM VARCHAR2(16)

KSMCHPTR RAW(4)

KSMCHSIZ NUMBER

KSMCHCLS VARCHAR2(8)

KSMCHTYP NUMBER

KSMCHPAR RAW(4)

Description of chunk type

Address of chunk

Size including header

Class●Perm●Recreate●Freeable●Free●R-Free●R-Freeable

Address of parent

Type (recreate only)●0x18 - KGL Handle●0x24 - Fixed Allocation●0x74 - KQR PO●0x80 - KQR SO●0xFFF - Extended header

37


Heap Dumps Heaps can be dumped using

ALTER SESSION SET EVENTS‘immediate trace name heapdump level <level>’;

where <level> is

Heap Summary Detail

PGA 1 1025

SGA 2 2050

UGA 4 4100

CGA – Current Call 8 8200

CGA – User Call 16 16400

LGA – Large Pool 32 32800

38


Free List Heap free lists contain 255 buckets

Each bucket contains double linked list to free chunks

Bucket sizes increase in increments of 4 bytes - 16, 20, 24, 28, 32 ... 808, 812 increments of 64 bytes - 876, 940, 1004 ... 3948, 4012 then 4108, 8204, 16396, 32780, 65548

Reduces fragmentation

39


Free List Example

16

Heap Header

52 byte chunks

24 byte chunks20

24

28

32

36

40

44

48

52

56

60

64

Buckets

36 byte chunks

40


Subheaps Heaps can contain subheaps Objects can have up to 10 subheaps

SQL statements include subheaps 0 and 6

Subheaps consist of one or more extents Subheaps have heap headers

Subheap header format similar to heap header format Only one freelist containing all free space

SubheapHeader

FreeList

Extent 0 Extent 1 Extent 2

Chunk

41


Subheap Dumps In Oracle 9.0.1 and below to dump a subheap, first obtain the

address of the subheap and convert to decimal

0x56b95c0c = 1454988300

For a summary dump use

For a detailed dump add 1 to the address e.g.

ALTER SESSION SET EVENTS ‘immediate trace name heapdump_addr level 1, addr 0x56b95c0c’;


ALTER SESSION SET EVENTS ‘immediate trace name heapdump_addr level 1454988300’;

ALTER SESSION SET EVENTS ‘immediate trace name heapdump_addr level 1454988301’;

In Oracle 9.2 and above to dump the subheap summary use

For a detailed dump use

42


Subheap Dumps Example - dump the SGA using

Chunk 56b94dc8 sz= 304 recreate "KGL handles " latch=0x56efd918Chunk 56b94ef8 sz= 560 freeable "library cache " ds=0x56b95c0cChunk 56b95128 sz= 540 recreate "KQR PO " latch=(nil)Chunk 56b95344 sz= 540 recreate "KQR PO " latch=0x56d719f4Chunk 56b95560 sz=1116 freeable "KGLS heap " ds=0x56b96d1cChunk 56b959bc sz= 20 free " "Chunk 56b959d0 sz= 560 recreate "library cache " latch=(nil) ds 56b95c0c sz=1120 ct= 2

56b94ef8 sz= 560Chunk 56b95c00 sz= 96 freeable "library cache "

Chunk 56b94dc8 sz= 304 recreate "KGL handles " latch=0x56efd918Chunk 56b94ef8 sz= 560 freeable "library cache " ds=0x56b95c0cChunk 56b95128 sz= 540 recreate "KQR PO " latch=(nil)Chunk 56b95344 sz= 540 recreate "KQR PO " latch=0x56d719f4Chunk 56b95560 sz=1116 freeable "KGLS heap " ds=0x56b96d1cChunk 56b959bc sz= 20 free " "Chunk 56b959d0 sz= 560 recreate "library cache " latch=(nil) ds 56b95c0c sz=1120 ct= 2

56b94ef8 sz= 560Chunk 56b95c00 sz= 96 freeable "library cache "

ALTER SESSION SET EVENTS ‘immediate trace name heapdump level 2’;

Dump subheap using


43


Subheap DumpsHEAP DUMP heap name="library cache" desc=0x576193c4 extent sz=0x224 alt=32767 het=16 rec=9 flg=2 opc=2 parent=0x5000002c owner=0x5761826c nex=(nil) xsz=0x224EXTENT 0 addr=0x57615130 Chunk 57615138 sz= 312 perm "perm " alo=260 Chunk 57615270 sz= 76 freeable "kgltbtab " Chunk 576152bc sz= 76 freeable "kgltbtab " Chunk 57615308 sz= 76 freeable "kgltbtab "EXTENT 1 addr=0x57616a88 Chunk 57616a90 sz= 512 perm "perm " alo=512 Chunk 57616c90 sz= 28 free " "EXTENT 2 addr=0x57618254 Chunk 5761825c sz= 172 perm "perm " alo=172 Chunk 57618308 sz= 36 free " "Total heap size = 1288

FREE LISTS: Bucket 0 size=0 Chunk 57616c90 sz= 28 free " " Chunk 57618308 sz= 36 free " "Total free space = 64UNPINNED RECREATABLE CHUNKS (lru first):PERMANENT CHUNKS: Chunk 57615138 sz= 312 perm "perm " alo=260 Chunk 57616a90 sz= 512 perm "perm " alo=512 Chunk 5761825c sz= 172 perm "perm " alo=172Permanent space = 996

Extent 0

Extent 1

Extent 2

Free List

44


X$KSMHP Externalises chunks in a subheap

ADDR RAW(4)

INDX NUMBER

INST_ID NUMBER

KSMCHDS RAW(4)


KSMCHPTR RAW(4)

KSMCHSIZ NUMBER


KSMCHTYP NUMBER

KSMCHPAR RAW(4)

KSMCHOWN RAW(4) Address of parent heap

Address of data segment

Description of chunk type

Address of chunk

Size including header

Class●Perm●Free

45


X$KSMHP

SQL> SELECT COUNT(*) FROM x$ksmhp;

0 rows

SQL> SELECT COUNT(*) FROM x$ksmhpWHERE ksmchds = HEXTORAW ('5755E798');

COUNT(*)-------- 1

SQL> SELECT kglobhd6 FROM x$kglobWHERE kglnaobj = 'SELECT SUM(c1) FROM t1'AND kglhdadr != kglhdpar;

KGLOBHD6--------5755E798

SQL> SELECT COUNT(*) FROM x$ksmhp;

COUNT(*) -------- 0

STOP

46


Library Cache Database objects

Tables Views Packages Functions

Shared cursors SQL statements Anonymous PL/SQL block Stored PL/SQL procedures and functions Java stored procedures Methods

47


Library Cache For example

SELECT SUM(c2)FROM t1WHERE c3 = 42AND c4 < 2004;

0 SELECT STATEMENT1 0 SORT (AGGREGATE)2 1 TABLE ACCESS (BY INDEX ROWID) OF 'T1'3 2 INDEX (RANGE SCAN) OF 'I2'

CREATE TABLE t1(

c1 NUMBER,c2 NUMBER,c3 NUMBER,c4 NUMBER

);

CREATE INDEX i1 ON t1 (c1);

CREATE INDEX i2 ON t1 (c3);

STOP

48


Library Cache

struct kgsms

ksmgsg_Heap

LibraryCache

KGLHD KGLHD KGLHD KGLHD

Anonymous List

KGLHD

KGLHD

KGLHD

KGLHD

512 x 1 wordpointers

256 x DLL headers

Library Cache Object Handle

512 x 256 = 131072 buckets

STOP

49


Library Cache Object - Parent

16 x 1 wordpointers

KGLHD

ParentObject

KGLNA

SELECT SUM (c2) FROM t1WHERE c3 = 42 AND c4 < 2004

ParentName

ChildHandle

KGLHD

Child 1

Child 2

Heap 0

KGLOB

X$KGLOB

ParentHandle

KGLHD

STOP

50


Library Cache Object - Child

KGLHD

ChildHandle

ChildObject

SELECTStatement

Heap 6

KGLOB

SubheapHeader

SubheapHeader

Heap 0

SubqueryHeader

Statisticsetc

X$KGLOB

STOP

51


Library Cache - Statement

SubqueryHeader

OperationExplain

PlanSORT

(AGGREGATE)

ExplainPlan

ExplainPlan

Operation TABLE ACCESS (BY INDEX ROWID)

Operation INDEX(RANGE SCAN)

STOP

52


Sort (Aggregate)

SORT (AGGREGATE)Output Columns

Column DefinitionObj =1234

Col=2

Column AliasAlias=C2

Expression

Function ExpressionOp=SUM

Column Expression

Expression

Variable

STOP

53


Table Access (By Index Rowid)


Col=2


Col=4


Expression

Function ExpressionOp=LT

Column Expression Constant Expression

ConstantValue=2004

ExpressionExpression

Variable

Variable

TABLE ACCESS (BY INDEX ROWID)Output

ColumnsPredicatec4 < 2004

Condition


Col=ROWID

Table AliasAlias=T1

Column Expression

Expression

Variable

ROWIDExpression

STOP

54


Index (Range Scan)


Col=ROWID


Col=3


Expression Array

Expression

Function ExpressionOp=EQ

Column Expression Constant Expression

ConstantValue=42

ExpressionExpression

Variable

INDEX (RANGE SCAN)Output

ColumnsPredicate

c3 = 42

Variable

STOP

55


Shared Pool Reserved Area Area of memory reserved for large contiguous requests for

memory Reduces fragmentation in shared pool Only used if no space available in shared pool Summarised in V$SHARED_POOL_RESERVED

SHARED_POOL_RESERVED_SIZE specifies size of shared pool in bytes defaults to 5% of SHARED_POOL_SIZE

_SHARED_POOL_RESERVED_PCT specifies percentage of shared pool to reserve defaults to 5%

_SHARED_POOL_RESERVED_MIN_ALLOC specifies minimum chunk size e.g. 4400

56


X$KSMSPR Externalises address, size and class of all chunks in the

shared pool

ADDR RAW(4)

INDX NUMBER

INST_ID NUMBER


KSMCHPTR RAW(4)

KSMCHSIZ NUMBER


KSMCHTYP NUMBER

KSMCHPAR RAW(4)

Comment● free memory● reserved_stopper

Address

Size in bytes

Class●R-free●R-freeable

57


Shared Pool Reserved AreaSELECT ksmchcom,ksmchptr,ksmchsiz,ksmchcls

FROM x$ksmsprORDER BY ksmchptr;

KSMCHCOM KSMCHPTR KSMCHSIZ KSMCHCLS

reserved_stopper 56400024 20 R-freeable

free memory 56400038 126900 R-free

reserved_stopper 5641EFEC 20 R-freeable




reserved_stopper 56C00024 20 R-freeable

free memory 56C00038 126900 R-free

reserved_stopper 56C1EFEC 20 R-freeable


KSMCHCOM KSMCHPTR KSMCHSIZ KSMCHCLS







reserved_stopper 56C00024 20 R-freeable

free memory 56C00038 126900 R-free

reserved_stopper 56C1EFEC 20 R-freeable


56400000

56800000

56C00000

57000000

57400000

57800000

57C00000

58000000

STOP

58


Log Buffer

2 x 4K guard pages (DEADFACE)

1288 x 512 byte blocks for redo

Each 512 byte includes 16 byte header

Usable redo = 1288 x 496 = 638848 bytes

LOG_BUFFER = 524288

Guard Page

Guard Page

Header - 16 bytes

Body - 496 bytes

58400000

584A2000

STOP

59


Thank you for your interest

For more information and to provide feedback

please contact me

My e-mail address is:[email protected]

My website address is:

www.juliandyke.com

Documents

1 Julian Dyke Independent Consultant © 2005 Julian Dyke SGA Internals Web Version juliandyke.com