6 Oracle深度學習筆記——內存架構之SGA 概述
6.Oracle深度學習筆記——內存架構之SGA 概述
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SGA和後臺進程一起組成數據庫實例。所有服務進程代表用戶可以從SGA中讀取信息。在數據庫操作的時候，多個服務進程寫到SGA中。
PS：服務和後臺進程的內存並沒有分配在SGA中個，而是在另外獨立的內存空間。
每個數據塊實例有自己的SGA。在實例啟動的時候數據庫自動分配SGA，在實例關閉的時候回收內存。
啟動時候如下：
idle> startup
ORACLE instance started.
Total SystemGlobal Area 1140850688 bytes
Fixed Size 2923584 bytes
Variable Size 419431360 bytes
Database Buffers 704643072 bytes
Redo Buffers 13852672 bytes
Database mounted.
Database opened.
啟動實例，分配內存。
SGA有很多內存組件，分配用於特定的目的。
所有組件除了REDOLOG BUFFER，都是通過連續的內存單位叫做granules來分配的。
Granule大小和平臺、總的SGA大小相關。
可以查看V$SGASTAT視圖來查看相關信息，如下：
sys@PDB1> select * from v$sgastat;
POOL NAME BYTES CON_ID
------------ ------------------------------------ ----------
fixed_sga 2923584 0
buffer_cache 721420288 0
log_buffer 13852672 0
shared_io_pool 50331648 0
shared pool modification hash table c 163840 3
shared pool KQR S SO 1800 3
shared pool monitoring column usage e 4160 3
shared pool qmpspdbonfy:0 65280 3
shared pool KGLDA 253512 3
shared pool kglsim object batch 81144 3
shared pool PDBHP 4464176 3
shared pool KOKTD 7344 3
shared pool kwqicaqe2kc1 17616 3
shared pool PRTDS 12144 3
shared pool parameter table block 31832 3
shared pool KGLH0 5049432 3
shared pool KGLNA 136 3
shared pool call 15320 3
shared pool free memory 54148480 0
shared pool KCB tablespace encryption 1440 3
shared pool SQLP 333544 3
shared pool kkcnRstatIni 680 3
shared pool kwqmncgr: allocate buffer 4112 3
shared pool PLDIA 435568 3
shared pool pdb event stats 1056000 3
shared pool PDB Heap Descriptor 136 3
shared pool KKBTD 14528 3
shared pool KQR L PO 2126464 3
shared pool PRTMV 2432 3
shared pool SQLA 6110336 3
shared pool parameter handle 4168 3
shared pool KQR M PO 97888 3
shared pool SQLK 16192 3
shared pool KKSSP 42256 3
shared pool KKTIN 9552 3
shared pool kwssnmapAlloc 6800 3
shared pool KGLS 3003880 3
shared pool kglsim heap 59520 3
shared pool ksu:ksunf_freelist 4032 3
shared pool KGLHD 816600 3
shared pool KQR M SO 32304 3
shared pool KQR X PO 180192 3
shared pool object queue header free 33280 3
shared pool KQR X SO 1349792 3
large pool free memory 32301056 0
java pool free memory 16777216 0
46 rows selected.
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6 Oracle深度學習筆記——內存架構之SGA 概述