SGA_TARGET

Property Description

Parameter type

Big integer

Syntax

SGA_TARGET = integer [K | M | G]

Default value

0 (SGA autotuning is disabled for DEFERRED mode autotuning requests, but allowed for IMMEDIATE mode autotuning requests)

Modifiable

ALTER SYSTEM

Range of values

64 MB to operating system-dependent

Basic

Yes

SGA_TARGET specifies the total size of all SGA components. If SGA_TARGET is specified, then the following memory pools are automatically sized:

  • Buffer cache (DB_CACHE_SIZE)

  • Shared pool (SHARED_POOL_SIZE)

  • Large pool (LARGE_POOL_SIZE)

  • Java pool (JAVA_POOL_SIZE)

  • Streams pool (STREAMS_POOL_SIZE)

If these automatically tuned memory pools are set to nonzero values, then those values are used as minimum levels by Automatic Shared Memory Management. You would set minimum values if an application component needs a minimum amount of memory to function properly.

The following pools are manually sized components and are not affected by Automatic Shared Memory Management:

  • Log buffer

  • Other buffer caches, such as KEEP, RECYCLE, and other block sizes

  • Fixed SGA and other internal allocations

The memory allocated to these pools is deducted from the total available for SGA_TARGET when Automatic Shared Memory Management computes the values of the automatically tuned memory pools.

In the Default value field, IMMEDIATE mode autotuning requests are necessary to avoid ORA-04031 errors. The DEFERRED and IMMEDIATE modes are reflected in the OPER_MODE column of the V$MEMORY_RESIZE_OPS view.

If Automatic Memory Management is enabled (MEMORY_TARGET is set to a positive value) and SGA_TARGET is also set to a positive value, the SGA_TARGET value acts as the minimum value for the size of the SGA.

See Also: