Skip to main content

How to reset sga_max_size

Today I decided to increase memory but before that I wanted to change sga_max_size`s value.

Because in my production database configured sga_max_size to 12Gb.

It means independing on busy or idle of instance state, SGA could not be more than 12GB (it is worse).
The SGA_MAX_SIZE specifies the maximum size of the SGA for the lifetime of the instance.

Our instance configured AMM:

select name, value from v$parameter where name like 'memory%'  

memory_target    32212254720
memory_max_target    32212254720

--Checking init file

-bash-3.2$ more initPROD.ora| grep -i sga
PROD.__sga_target=12616466432
*.sga_max_size=25769803776
*.sga_target=0
-bash-3.2$

SGA_MAX_SIZE is not dynamic value, after changing those value, you should restart instance.

SQL> show parameter sga

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
lock_sga                             boolean     FALSE
pre_page_sga                         boolean     FALSE
sga_max_size                         big integer 12G
sga_target                           big integer 0

SQL> alter system set sga_max_size=0 scope=spfile;

System altered.

SQL> shut immediate
Database closed.
Database dismounted.
ORACLE instance shut down.

SQL> startup
ORACLE instance started.

Total System Global Area 1,2828E+10 bytes
Fixed Size                  2272944 bytes
Variable Size            6710886736 bytes
Database Buffers         6106906624 bytes
Redo Buffers                7602176 bytes
Database mounted.
Database opened.

SQL> show parameter sga

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
lock_sga                             boolean     FALSE
pre_page_sga                         boolean     FALSE
sga_max_size                         big integer 12G
sga_target                           big integer 0

SQL> show parameter spfile

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
spfile                               string      /u01/app/oracle/product/11.0.1/db_1/dbs/spfilePROD.ora


Uppps! Nothing is changed!

-bash-3.2$ cd /u01/app/oracle/product/11.0.1/db_1/dbs/
-bash-3.2$ more spfilePROD.ora | grep sga
PROD.__sga_target=12276727808
*.sga_max_size=0
*
-bash-3.2$

As you see spfile changed but Oracle set this parameter itself.

After that I investigated from the internet and found interesting post from Tom Kyte.

http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:1137385000346840516

"You are using automatic memory management, we set things - the caches, everything, to whatever we feel like.
If you set memory_target, you need set nothing else. Just don't set it at all. Unset it."


If you want to set sga_max_size turn of memory parameters then set sga_max_size.

Comments

Post a Comment

Popular posts from this blog

Fix ORA-01139: RESETLOGS option only valid after an incomplete database recovery

While shutting down my TEST database process was hanged. Then I had to use shutdown abort. But when I wanted to start database it did not open. SQL> select name from v$database; NAME --------- TEST SQL> shut abort; ORACLE instance shut down. SQL> startup mount ORACLE instance started. Total System Global Area 6597406720 bytes Fixed Size 2265664 bytes Variable Size 3204451776 bytes Database Buffers 3372220416 bytes Redo Buffers 18468864 bytes Database mounted. SQL> alter database open; alter database open * ERROR at line 1: ORA-03113: end-of-file on communication channel Process ID: 6552 Session ID: 191 Serial number: 3  What`s wrong?  SQL> alter database open resetlogs; ERROR:    ORA-03114: not connected to ORACLE    SQL> exit Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Pr...
9 comments
Read more

Fix: ORA-13639: The current operation was interrupted because it timed out.

Sometimes SQL Tuning Advisor interrupts cause time limit took more than defined. You have to analyze it or increase value. Here you can see increasing of value. Example result of sql select                  execution_name, advisor_name,                  to_char(execution_start,'dd-mon-yy hh:mi:ss') execution_start,                  to_char(execution_end,'dd-mon-yy hh:mi:ss') execution_end, status,error_message from dba_advisor_executions where task_name = 'SYS_AUTO_SQL_TUNING_TASK' order by execution_start; Check value of TIME_LIMIT`s parameter : SQL> column parameter_value for A35 SQL> select parameter_name, parameter_value from dba_advisor_parameters where task_name = 'SYS_AUTO_SQL_TUNING_TASK' and parameter_name in ('TIME_LIMIT', 'DEFAULT_EXECUTION_TYP...
Post a Comment
Read more

How to fix ORA-26040: Data block was loaded using the NOLOGGING option

Today I faced with new ORA error. After solving I want to share this experience with yours. So, today 5`th datafile of my database was corrupted (/u01/app/oracle/oradata/ulfet_db/example01.dbf). After recover via RMAN I saw strange error. RMAN> recover datafile 5 block 443; Starting recover at 24-MAR-13 using channel ORA_DISK_1 channel ORA_DISK_1: restoring block(s) channel ORA_DISK_1: specifying block(s) to restore from backup set restoring blocks of datafile 00005 channel ORA_DISK_1: reading from backup piece /u01/app/oracle/flash_recovery_area/ULFET_DB/backupset/2013_03_24/o1_mf_nnndf_TAG20130324T223233_8nykp220_.bkp channel ORA_DISK_1: piece handle=/u01/app/oracle/flash_recovery_area/ULFET_DB/backupset/2013_03_24/o1_mf_nnndf_TAG20130324T223233_8nykp220_.bkp tag=TAG20130324T223233 channel ORA_DISK_1: restored block(s) from backup piece 1 channel ORA_DISK_1: block restore complete, elapsed time: 00:00:03 starting media recovery media recovery complete, elapsed ti...
2 comments
Read more