USE_LARGE_PAGES

USE_LARGE_PAGES is used to manage the database’s use of large pages for SGA memory.

Note:

USE_LARGE_PAGES is supported on multiple operating systems. Setting this parameter to FALSE can make access to SGA memory slower.

Exception: USE_LARGE_PAGES is automatically set to FALSE when Automatic Memory Management is used on Linux platforms. This setting does not cause performance degradation.

Property	Description
Parameter type	String
Syntax	USE_LARGE_PAGES = { TRUE | FALSE | AUTO | ONLY | AUTO_ONLY }
Default value	ONLY for Exadata Database Service in the cloud, Base Database Service in the cloud, and databases created using Exadata automation tools such as Oracle Exadata Deployment Assistant (OEDA) and OEDA Command Line Utility (OEDACLI) AUTO_ONLY for all other Exadata systems TRUE for all other systems
Modifiable	No
Modifiable in a PDB	No
Basic	No
Oracle RAC	Multiple instances can use different values

Values

These values can be specified for USE_LARGE_PAGES:

• TRUE

  Specifies that the instance can use large pages if large pages are configured on the system.

  In Oracle Database 11g Release 2 (11.2.0.2), if there are not enough large pages configured on the system, then regular sized pages will be used to allocate SGA memory. This can cause the free large pages to go unused, and the operating system can allocate a huge amount of memory to create page tables to map SGA into physical pages for the Oracle processes. This may lead to ORA-04030 errors and severe performance degradation on an instance.

  In Oracle Database 11g Release 2 (11.2.0.3) and later releases, Oracle allocates as much of the SGA as it can in large pages, and if it runs out, it will allocate the rest of the SGA using regular sized pages. This can cause the instance to create additional shared memory segments for the SGA, but the total SGA size will be unchanged. In this supported mixed page mode allocation, the database will exhaust the available large pages before switching to regular sized pages.

• FALSE

  Specifies that the instance will not use large pages. This setting is not recommended because it can cause severe performance degradation for the instance. Although the USE_LARGE_PAGES initialization parameter applies only to Linux systems, setting this parameter to FALSE can cause performance degradation on any platform.

• AUTO

  Specifies that, during startup, the instance will calculate and request the number of large pages it requires. If the operating system cannot fulfill this request, then the instance will start with a combination of large and regular pages.

• ONLY

  Specifies that the instance will fail to start if large pages cannot be used for the entire SGA memory. Oracle recommends this setting for consistent performance. This setting is the default setting for Exadata Database Service in the cloud and Base Database Service in the cloud.

  When USE_LARGE_PAGES is set to ONLY, you must not explicitly set values for MEMORY_TARGET and MEMORY_MAX_TARGET in the initialization parameter file. Doing so will prevent the instance from starting.

• AUTO_ONLY

  Specifies that, during startup, the instance will calculate and request the number of large pages it requires. If the operating system can fulfill this request, then the instance will start successfully. If the operating system cannot fulfill this request, then the instance will fail to start. This ensures that no instances will run with under-provisioned large pages. This setting is available starting with Oracle Database 19c and it is the default setting for on-premises Exadata systems.

See Also:

• “MEMORY_TARGET”

• “MEMORY_MAX_TARGET”