Shmmax, linuxshmmax

Shmmax, linuxshmmax
The shmmax Kernel Parameter defines the maximum value of a single shared memory segment allowed by the system.
Now the shmmax simulation settings are small:
[Root @ localhost kernel] # cat/etc/redhat-release
Red Hat Enterprise Linux Server release 5.5 (Tikanga)

SQL> select * from v $ version where rownum = 1;

BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0-Production


[Root @ localhost ~] # Cd/proc/sys/kernel | echo 1000> shmmax => note: the modification will expire after the OS is restarted.





[Oracle @ localhost ~] $ Sqlplus/as sysdba


SQL * Plus: Release 11.2.0.1.0 Production on Sunday May 10 23:27:36 2015


Copyright (c) 1982,200 9, Oracle. All rights reserved.


ERROR:
ORA-12547: TNS: Lost connection


Enter the User Name:


Alarm log:
......
......
Sun May 10 23:27:42 2015
Process J000 died, see its trace file
Kkjcre1p: unable to spawn jobq slave process
Errors in file/u01/app/oracle/diag/rdbms/orcl3939/orcl3939/trace/orcl3939_cjq0_10511.trc:
Process J000 died, see its trace file
Kkjcre1p: unable to spawn jobq slave process
Errors in file/u01/app/oracle/diag/rdbms/orcl3939/orcl3939/trace/orcl3939_cjq0_10511.trc:


/U01/app/oracle/diag/rdbms/orcl3939/orcl3939/trace/orcl3939_cjq0_10511.trc:

Trace file/u01/app/oracle/diag/rdbms/orcl3939/orcl3939/trace/orcl3939_cjq0_10511.trc
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0-Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
ORACLE_HOME =/u01/app/oracle/product/11.2.0/dbhome_1
System name: Linux
Node name: localhost. localdomain
Release: 2.6.18-194. el5
Version: #1 SMP Mon Mar 29 20:06:41 EDT 2010
Machine: i686
Instance name: orcl3939
Redo thread mounted by this instance: 1
Oracle process number: 25
Unix process pid: 10511, image: oracle@localhost.localdomain (CJQ0)




* ** 23:08:21. 485
* ** Session id: (133.9) 23:08:21. 485
* ** Client id :() 23:08:21. 485
* ** Service name :( SYS $ BACKGROUND) 23:08:21. 485
* ** Module name :() 23:08:21. 485
* ** Action name :() 23:08:21. 485
 
Setting Resource Manager plan SCHEDULER [0x3009]: DEFAULT_MAINTENANCE_PLAN via scheduler window
Setting Resource Manager plan DEFAULT_MAINTENANCE_PLAN via parameter


* ** 23:27:42. 805
Process J000 is dead (pid = 11060 req_ver = 3 cur_ver = 3 state = KSOSP_SPAWNED ).


* ** 23:27:43. 876
Process J000 is dead (pid = 11063 req_ver = 16 cur_ver = 16 state = KSOSP_SPAWNED ).


* ** 23:28:43. 621
Process J000 is dead (pid = 11106 req_ver = 5 cur_ver = 5 state = KSOSP_SPAWNED ).


* ** 23:28:44. 743
Process J000 is dead (pid = 11109 req_ver = 17 cur_ver = 17 state = KSOSP_SPAWNED ).


* ** 23:34:43. 874
Process J000 is dead (pid = 11244 req_ver = 6 cur_ver = 6 state = KSOSP_SPAWNED ).


* ** 23:34:44. 888
Process J000 is dead (pid = 11247 req_ver = 18 cur_ver = 18 state = KSOSP_SPAWNED ).


* ** 23:35:42. 550
Process J000 is dead (pid = 11280 req_ver = 7 cur_ver = 7 state = KSOSP_SPAWNED ).


* ** 23:35:43. 565
Process J000 is dead (pid = 11285 req_ver = 19 cur_ver = 19 state = KSOSP_SPAWNED ).


[Oracle @ localhost ~] $ Ipcs-


------ Shared Memory Segments --------
Key shmid owner perms bytes nattch status
0x00000000 3276801 oracle 600 393216 2 dest
0x00000000 3309571 oracle 600 393216 2 dest
0x00000000 3342340 oracle 600 393216 2 dest
0x00000000 3375109 oracle 600 393216 2 dest
0x00000000 3407878 oracle 600 393216 2 dest
0x00000000 3440647 oracle 600 393216 2 dest
0x00000000 3473416 oracle 600 393216 2 dest
0x00000000 3506185 oracle 600 393216 2 dest
0x00000000 3538954 oracle 600 393216 2 dest
0x00000000 3571723 oracle 600 393216 2 dest
0x05a35eec 4194316 oracle 660 4096 0
0x038880a0 3735567 oracle 755 1079228 0


------ Semaphore Arrays --------
Key semid owner perms nsems
0xed251740 622592 oracle 660 154


------ Message Queues --------
Key msqid owner perms used-bytes messages


SQL> select * from v $ sgainfo;


NAME BYTES RES
---------------------------------------------
Fixed SGA Size 1336960 No
Redo Buffers 6094848 No
Buffer Cache Size 79691776 Yes
Shared Pool Size 176160768 Yes
Large Pool Size 4194304 Yes
Java Pool Size 4194304 Yes
Streams Pool Size 4194304 Yes
Shared IO Pool Size 0 Yes
Granule Size 4194304 No
Maximum SGA Size 422670336 No
Startup overhead in Shared Pool 58720256 No

NAME BYTES RES
---------------------------------------------
Free SGA Memory Available 146800640



If the shmmax size is smaller than the SGA setting, sga can be created successfully, but multiple shared memory segments will be allocated, but the shmmax size must have a bottom line,
Otherwise, the OS resource is exhausted, and Process J000 is dead
Generally, we recommend that you set shmmax to a higher value and restrict the sga to a shared memory segment.

Official documentation:
Memory Resources

The resources provided by the UNIX default kernels are often inadequate for a medium or large instance of Oracle Database. the maximum size of a shared memory segment (SHMMAX) and maximum number of semaphores available (SEMMNS) may be too low for Oracle Database recommendations.
Resources provided by the default UNIX kernel are usually insufficient medium or large database instances. The size of the maximum shared memory segment (SHMMAX) and the maximum number of available semaphores (SEMMNS) may be too low for Oracle databases.

On Windows, fewer resources are needed for interprocess communication (IPC), because the Oracle Database relational database management system is thread-based and not process-based. these resources, including shared memory and semaphores, are not adjustable by the user.

In Windows, fewer resources are required for inter-process communication (IPC), because the Oracle database's relational database management system is thread-based rather than process. These resources, including shared memory and semaphores, cannot be modified by users.