OracleStudy case-view the "strange phenomenon" of shared memory through IPCS"

OracleStudy case-view shared memory through IPCS "strange phenomenon" in Oracle11gR2 environment, through ipcs command to view shared memory, it was found that the memory allocated to Oracle is only 4096 Bytes, this problem has never been found in the Oracle10g environment! [Root @ rh6 ~] # Ipcs-a ------ SharedMemorySegments -------- keyshm

Oracle Study Case-view shared memory through IPCS "strange phenomenon" in Oracle 11gR2 environment, through the ipcs command to view the shared memory, it was found that the memory allocated to Oracle is only 4096 Bytes, this problem has never been found in Oracle 10 Gb environment! [Root @ rh6 ~] # Ipcs-a ------ SharedMemorySegments -------- keyshm

Case Study of Oracle Study-view the "strange phenomenon" of shared memory through IPCS"

In the Oracle 11gR2 environment, using the ipcs command to view the shared memory, we found that the memory allocated to Oracle is only 4096 Bytes, and this problem was never found in the Oracle 10g environment!

[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

Database Version:

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

The following two parameters are used to automatically manage the memory of cycle 11g:

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

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1. Will it be related to the memory_max_target parameter? Set it to 0 and restart the database.

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.

Let's look at the shared memory:

[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

We found that the shared memory allocated to Oracle is still small, which does not seem to be a problem with the memory_target parameter!

2. Try to adjust the memory_max_target parameter and restore it to the default value of the system:

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

View the system shared memory:

[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

It seems that the memory_max_target parameter is set. As a result, the memory allocated to Oracle is 4096 Bytes through ipcs!