PGA_AGGREGATE_LIMIT

PGA_AGGREGATE_LIMIT specifies a limit on the aggregate PGA memory consumed by the instance.

Property	Description
Parameter type	Big integer
Syntax	PGA_AGGREGATE_LIMIT = integer [K | M | G]
Default value	If MEMORY_TARGET is set, then PGA_AGGREGATE_LIMIT defaults to the MEMORY_MAX_TARGET value. If MEMORY_TARGET is not set, then PGA_AGGREGATE_LIMIT defaults to 200% of PGA_AGGREGATE_TARGET. If MEMORY_TARGET is not set, and PGA_AGGREGATE_TARGET is explicitly set to 0, then the value of PGA_AGGREGATE_LIMIT is set to 90% of the physical memory size minus the total SGA size. In all cases, the default PGA_AGGREGATE_LIMIT is at least 2GB and at least 3MB times the PROCESSES parameter (and at least 5MB times the PROCESSES parameter for an Oracle RAC instance). For a PDB, the default value is the same as the CDB's default value.
Modifiable	ALTER SYSTEM
Modifiable in a PDB	Yes
Range of values	Do not attempt to set PGA_AGGREGATE_LIMIT below its default value, even in a parameter file (pfile), or instance startup will fail. However, PGA_AGGREGATE_LIMIT can be set to 0 either in a parameter file or dynamically after startup. If a value of 0 is specified, it means there is no limit to the aggregate PGA memory consumed by the instance.
Basic	No

Actions Taken When PGA_AGGREGATE_LIMIT is Exceeded

Parallel queries will be treated as a unit. First, the sessions that are using the most untunable memory will have their calls terminated. Then, if the total PGA memory usage is still over the limit, the sessions that are using the most untunable memory will be terminated.

SYS processes and background processes other than job queue processes will not be subjected to any of the actions described in this section. Instead, if they are using the most untunable memory, they will periodically write a brief summary of their PGA usage to a trace file.

Note: This parameter is optional for pluggable databases (PDBs). When this parameter is set for a PDB, it specifies the maximum PGA size for the PDB.

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.

• You must set the PGA_AGGREGATE_LIMIT initialization parameter in a PDB to a value that meets these requirements:

  • Less than or equal to the PGA_AGGREGATE_LIMIT value set at the CDB level

  • Greater than or equal to twice the value of PGA_AGGREGATE_TARGET set in the PDB

  When you set PGA_AGGREGATE_LIMIT in a PDB to a value that does not meet these requirements, you receive an error. If these requirements are violated after the PDB’s parameter is set (for example, if the PGA_AGGREGATE_LIMIT value is changed at the CDB level), Oracle will adjust the PDB’s value to meet these requirements.

See Also:

• “MEMORY_TARGET”

• “PGA_AGGREGATE_TARGET”

• Oracle AI Database Multitenant Administrator’s Guide for more information about the initialization parameters that control the memory usage of PDBs

• Oracle AI Database Performance Tuning Guide for more information about this parameter