1.317 SHARED_POOL_SIZE

SHARED_POOL_SIZE specifies (in bytes) the size of the shared pool.

Property Description

Parameter type

Big integer

Syntax

SHARED_POOL_SIZE = integer [K | M | G]

Default value

If SGA_TARGET is set: If the parameter is not specified, then the default is 0 (internally determined by the Oracle Database). If the parameter is specified, then the user-specified value indicates a minimum value for the memory pool.

If SGA_TARGET is not set (32-bit platforms): 64 MB, rounded up to the nearest granule size.

If SGA_TARGET is not set (64-bit platforms): 128 MB, rounded up to the nearest granule size.

For considerations when dealing with database instances using Oracle ASM, see "SHARED_POOL_SIZE and Automatic Storage Management".

Modifiable

ALTER SYSTEM

Modifiable in a PDB

Yes

Range of values

Minimum: the granule size

Maximum: operating system-dependent

Basic

No

The shared pool contains shared cursors, stored procedures, control structures, and other structures. If SGA_TARGET is not set, then Oracle also allocates parallel execution message buffers from the shared pool. Larger values improve performance in multiuser systems. Smaller values use less memory.

You can monitor utilization of the shared pool by querying the view V$SGASTAT.

Note:

This parameter is optional for pluggable databases (PDBs). When this parameter is set for a PDB, it guarantees the shared pool size for the PDB. When this parameter is not set at the PDB level, the PDB has no limit for the amount of shared pool it can use, other than the CDB's shared pool size.

To be able to use Resource Manager in a CDB to control the amount of memory each PDB can use:

  • The NONCDB_COMPATIBLE initialization parameter must be set to FALSE at the CDB level (in the root of the CDB).

  • The MEMORY_TARGET initialization parameter must not be set at the CDB level.

  • If the SGA_TARGET initialization parameter is not set, but the SHARED_POOL_SIZE initialization parameter is set at the CDB level, then the following requirements must be met:

    • The value of SHARED_POOL_SIZE set in a PDB must be less than or equal to 50% of the SHARED_POOL_SIZE value at the CDB level.

    • The sum of the SHARED_POOL_SIZE values across all the PDBs in the CDB must be less than or equal to 50% of the SHARED_POOL_SIZE value at the CDB level.

    When you set SHARED_POOL_SIZE in a PDB to a value that does not meet these requirements, you receive an error.

If SGA_TARGET is set at the CDB level, these requirements must be met:

  • The values of DB_CACHE_SIZE plus SHARED_POOL_SIZE in a PDB must be less than or equal to 50% of the PDB’s SGA_TARGET value.

  • The values of DB_CACHE_SIZE plus SHARED_POOL_SIZE in a PDB must be less than or equal to 50% of the SGA_TARGET value at the CDB level.

  • The sum of DB_CACHE_SIZE plus SHARED_POOL_SIZE across all the PDBs in a CDB must be less than or equal to 50% of the SGA_TARGET value at the CDB level.

If any of these three requirements above are not met, you will receive an error.

See Also:

SHARED_POOL_SIZE and Automatic Storage Management

On a database instance using Oracle Automatic Storage Management (Oracle ASM), additional memory is required to store extent maps. As a general guideline, you can aggregate the values from the following queries to obtain current database storage size that is either already on Oracle ASM or will be stored in Oracle ASM. Then determine the redundancy type that is used (or will be used), and calculate the value for SHARED_POOL_SIZE, using the aggregated value as input.

SELECT SUM(BYTES)/(1024*1024*1024) FROM V$DATAFILE;
SELECT SUM(BYTES)/(1024*1024*1024) FROM V$LOGFILE a, V$LOG b
WHERE a.group#=b.group#;
SELECT SUM(BYTES)/(1024*1024*1024) FROM V$TEMPFILE WHERE
status='ONLINE';

Additionally, keep the following guidelines in mind:

  • For disk groups using external redundancy:

    (Every 100G of space needs 1M of extra shared pool) + 2M

  • For disk groups using normal redundancy:

    (Every 50G of space needs 1M of extra shared pool) + 4M

  • For disk groups using high redundancy:

    (Every 33G of space needs 1M of extra shared pool) + 6M