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Sunday, May 4, 2008

Memory Management with 11G

Oracle Memory Managment now make easier with Oracle 11g.

In the previous release (Oracle10g) we need to set TWO parameter for automatic memory management.

1. SGA_TARGET = xxx G

2. PGA_AGGREGATE_TARGET = xxx G

then oracle will automatically allocated size for Buffer cache,Shared pool, large pool etc.

Now In Oracle 11g will reduce two parameter (SGA_TARGET, PGA_AGGREGATE_TARGET) and introduce one new parameter called "MEMORY_TARGET". Which use for SGA or PGA size configuration.

When we specify MEMORY_TARGET parameter for instance then we no need to specify SGA_TARGET or PGA_AGGREGATE_TARGET parameter for memory configuration. Oracle will automatically allocate memory for memory parameter.

How to enable automatic memory management?

As previous parameter SGA_MAX_SIZE in 11g also one new parameter MEMORY_MAX_TARGET which is maximum limit for instance memory for oracle database.

Current database is not configured for MEMORY_TARGET parameter

SQL> show parameter target
NAME TYPE VALUE

------------------------------------ ----------- ------

archive_lag_target integer 0

db_flashback_retention_target integer 1440

fast_start_io_target integer 0

fast_start_mttr_target integer 0

memory_max_target big integer 0

memory_target big integer 0

pga_aggregate_target big integer 25M

sga_target big integer 172M

1. First set MEMORY_MAX_TARGET parameter for maximum instance memory limit.

SQL> alter system set memory_max_target=200M scope=SPFILE;
System altered.

NOTE: memory_target=(sga_target+pga_aggregate_target)

2. Shutdown & startup database

SQL> shutdown immediate

SQL> startup

NOTE: ORA-00843: Parameter not taking MEMORY_MAX_TARGET into account, see alert log for more information

SQL> --Above error occur when MEMORY_MAX_TARGET parameter value is lower then SGA_MAX_SIZE parameter value. so either remove SGA_MAX_SIZE parameter or Increase MEMORY_MAX_TARGET parameter value

SQL> create pfile='c:\temp\init.ora' from spfile;
File created.
SQL> --after editing recreate new spfile.SQL> create spfile from pfile='c:\temp\init.ora';
File created.

SQL> startup

3. SET MEMORY_TARGET parameter to NON-ZERO & set "0" to SGA or PGA_AGGREGATE_TARGET parameter.

SQL> alter system set memory_target=200m;
System altered.
SQL> alter system set sga_target=0;
System altered.
SQL> alter system set pga_aggregate_target=0;
System altered.
SQL> show parameter target
NAME TYPE VALUE

------------------------------------ ----------- -----------archive_lag_target integer 0

db_flashback_retention_target integer 1440

fast_start_io_target integer 0

fast_start_mttr_target integer 0

memory_max_target big integer 200M

memory_target big integer 200M

pga_aggregate_target big integer 0

sga_target big integer 0

Monitoring and Tuning automatic memory management

New V$ view : V$MEMORY_DYNAMIC_COMPONENTS show the current size of SGA and PGA.

and New V$ view: v$MEMORY_TARGET_ADVICE provides advice for the memory_target init parameter

read more http://download.oracle.com/docs/cd/B28359_01/server.111/b28310/memory003.htm#BGBJAHEJ

2 comments:

marry said...

Blogs are so informative where we get lots of information on any topic. Nice job keep it up!!
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