[20210126]探究oracle内存分配3.txt

--//上午做了一番探究,继续测试,我手工增加log_buffer看看如何分配.

1.环境:
SYS@book> @ ver1
PORT_STRING                    VERSION        BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx            11.2.0.4.0     Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

SYS@book> show sga
Total System Global Area  643084288 bytes
Fixed Size                  2255872 bytes
Variable Size             205521920 bytes
Database Buffers          427819008 bytes
Redo Buffers                7487488 bytes

SYS@book> create pfile='/tmp/@.ora' from spfile ;
File created.

--//手工编辑/tmp/book.ora文件,修改log_buffer,仅仅比原来增加1个字节.
*.log_buffer=7487489

2.重启数据库:
SYS@book> shutdown immediate ;
Database closed.
Database dismounted.
ORACLE instance shut down.
SYS@book> startup pfile='/tmp/@.ora'
ORACLE instance started.

Total System Global Area  647278592 bytes
Fixed Size                  2255872 bytes
Variable Size             205521920 bytes
Database Buffers          427819008 bytes
Redo Buffers               11681792 bytes
Database mounted.
Database opened.
--//Redo Buffers =11681792
--// (11681792-7487488)/4/1024/1024 = 1 ,我仅仅增加1个字节,就增级1个GRANULE_SIZE=4m.

$ ipcs -m
------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status
0x00000000 30605314   oracle    640        16777216   23
0x00000000 30638083   oracle    640        633339904  23
0xe8a8ec10 30670852   oracle    640        2097152    23

$ cat /proc/$(ps -ef | grep smo[n]| awk '{print $2}')/maps | grep SYSV
60000000-61000000 rw-s 00000000 00:0b 30605314                           /SYSV00000000 (deleted)
61000000-86c00000 rw-s 00000000 00:0b 30638083                           /SYSV00000000 (deleted)
86c00000-86e00000 rw-s 00000000 00:0b 30670852                           /SYSVe8a8ec10 (deleted)

--//61000000 -60000000 = 16777216 .
--//占用4个GRANULE_SIZE.

--//Fixed Size+Redo Buffers = 2255872+11681792 = 13937664
--//13937664/4/1024/1024 = 3.322998046875