6.Oracle深度学习笔记——内存架构之SGA 概述
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SGA和后台进程一起组成数据库实例。所有服务进程代表用户可以从SGA中读取信息。在数据库操作的时候,多个服务进程写到SGA中。
PS:服务和后台进程的内存并没有分配在SGA中个,而是在另外独立的内存空间。
每个数据块实例有自己的SGA。在实例启动的时候数据库自动分配SGA,在实例关闭的时候回收内存。
启动时候如下:
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.
启动实例,分配内存。
SGA有很多内存组件,分配用于特定的目的。
所有组件除了REDOLOG BUFFER,都是通过连续的内存单位叫做granules来分配的。
Granule大小和平台、总的SGA大小相关。
可以查看V$SGASTAT视图来查看相关信息,如下:
sys@PDB1> select * from v$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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