oracle study之案例--通过ipcs查看共享内存之“怪现象” 在oracle 11gr2环境下，通过ipcs命令查看共享内存，竟然发现分配给oracle的内存只有4096bytes，而在oracle 10g环境下从未发现这种问题！ [root@rh6~]#ipcs-a------sharedmemorysegments--------keyshm
oracle study之案例--通过ipcs查看共享内存之“怪现象”   
       在oracle 11gr2环境下，通过ipcs命令查看共享内存，竟然发现分配给oracle的内存只有4096bytes，而在oracle 10g环境下从未发现这种问题！
[root@rh6 ~]# ipcs -a------ shared memory segments --------key shmid owner perms bytes nattch status0x00000000 0 root 644 52 20x00000000 32769 root 644 16384 20x00000000 65538 root 644 268 20x00000000 98307 gdm 600 393216 2 dest0x00000000 131076 gdm 600 393216 2 dest0x00000000 163845 gdm 600 393216 2 dest0x00000000 196614 gdm 600 393216 2 dest0x00000000 229383 gdm 600 393216 2 dest0x4b4218ec 557064 oracle 660 4096 0------ semaphore arrays --------key semid owner perms nsems0x00000000 0 root 600 10x00000000 98305 root 600 10x000000a7 327682 root 600 10xbe61d9cc 983043 oracle 660 154------ message queues --------key msqid owner perms used-bytes messages
数据库版本：
16:27:09 sys@ test3 >select * from v$version;banner--------------------------------------------------------------------------------oracle database 11g enterprise edition release 11.2.0.1.0 - productionpl/sql release 11.2.0.1.0 - productioncore 11.2.0.1.0 productiontns for linux: version 11.2.0.1.0 - productionnlsrtl version 11.2.0.1.0 - production
oraccle 11g的通过以下两个参数实现内存的自动个管理：
16:27:19 sys@ test3 >show parameter memname type value------------------------------------ ----------- ------------------------------hi_shared_memory_address integer 0memory_max_target big integer 300mmemory_target big integer 300mshared_memory_address integer 0
650) this.width=650; src=http://www.linuxidc.com/upload/2014_02/14021810205766.jpg alt=在oracle 11g中用看oracle的共享内存段---------ipcs width=581 vspace=5 style=max-width:90% />
1、会不会是参数memory_max_target有关系呢？把它设为0，然后重启数据库。
16:28:11 sys@ test3 >alter system set memory_target=0 ;system altered.16:36:44 sys@ test3 >show parameter memname type value------------------------------------ ---------------------- ------------------------------hi_shared_memory_address integer 0memory_max_target big integer 300mmemory_target big integer 0shared_memory_address integer 016:30:51 sys@ test3 >startup force ;oracle instance started.total system global area 313860096 bytesfixed size 1336232 bytesvariable size 205524056 bytesdatabase buffers 100663296 bytesredo buffers 6336512 bytesdatabase mounted.database opened.
再看共享内存：
[oracle@rh6 ~]$ ipcs -a------ shared memory segments --------key shmid owner perms bytes nattch status0x00000000 0 root 644 52 20x00000000 32769 root 644 16384 20x00000000 65538 root 644 268 20x4b4218ec 622600 oracle 660 4096 0------ semaphore arrays --------key semid owner perms nsems0xbe61d9cc 1114115 oracle 660 154------ message queues --------key msqid owner perms used-bytes messages
发现分配给oracle的共享内存仍然很小，看来不是memory_target 参数的问题！
2、尝试调整memory_max_target参数，将其恢复到系统默认值：
16:39:49 sys@ test3 >alter system set sga_max_size=300m scope=spfile;system altered.16:40:06 sys@ test3 >alter system reset memory_max_target scope=spfile sid='*';system altered.16:40:40 sys@ test3 >startup force nomount;oracle instance started.total system global area 313860096 bytesfixed size 1336232 bytesvariable size 205524056 bytesdatabase buffers 100663296 bytesredo buffers 6336512 bytes16:40:52 sys@ test3 >show parameter memname type value------------------------------------ ---------------------- ------------------------------hi_shared_memory_address integer 0memory_max_target big integer 0memory_target big integer 0shared_memory_address integer 016:40:59 sys@ test3 >show parameter sganame type value------------------------------------ ---------------------- ------------------------------lock_sga boolean falsepre_page_sga boolean falsesga_max_size big integer 300msga_target big integer 180m
查看系统共享内存:
[oracle@rh6 ~]$ ipcs -a------ shared memory segments --------key shmid owner perms bytes nattch status0x00000000 0 root 644 52 20x00000000 32769 root 644 16384 20x00000000 65538 root 644 268 20x4b4218ec 884744 oracle 660 316669952 16------ semaphore arrays --------key semid owner perms nsems0xbe61d9cc 1638403 oracle 660 154------ message queues --------key msqid owner perms used-bytes messages
看来是设置了memory_max_target参数的原因，导致通过ipcs查看到分配给oracle的内存为4096bytes！