MEMORY_TARGET

Property	Description
Parameter type	Big integer
Syntax	MEMORY_TARGET = integer [K | M | G]
Default value	0
Modifiable	ALTER SYSTEM
Range of values	152 MB to MEMORY_MAX_TARGET
Basic	No

MEMORY_TARGET specifies the Oracle system-wide usable memory. The database tunes memory to the MEMORY_TARGET value, reducing or enlarging the SGA and PGA as needed.

In a text-based initialization parameter file, if you omit MEMORY_MAX_TARGET and include a value for MEMORY_TARGET, then the database automatically sets MEMORY_MAX_TARGET to the value of MEMORY_TARGET. If you omit the line for MEMORY_TARGET and include a value for MEMORY_MAX_TARGET, the MEMORY_TARGET parameter defaults to zero. After startup, you can then dynamically change MEMORY_TARGET to a nonzero value, provided that it does not exceed the value of MEMORY_MAX_TARGET.

Note:

1. This parameter was introduced in 11g.

2. 11g MEMORY_TARGET Parameter Dependency

If MEMORY_TARGET is set to a non-zero value:

• If SGA_TARGET and PGA_AGGREGATE_TARGET are set, they will be considered the minimum values for the sizes of SGA and the PGA respectively. MEMORY_TARGET can take values from SGA_TARGET + PGA_AGGREGATE_TARGET to MEMORY_MAX_SIZE.
• If SGA_TARGET is set and PGA_AGGREGATE_TARGET is not set, we will still auto-tune both parameters. PGA_AGGREGATE_TARGET will be initialized to a value of (MEMORY_TARGET-SGA_TARGET).
• If PGA_AGGREGATE_TARGET is set and SGA_TARGET is not set, we will still auto-tune both parameters. SGA_TARGET will be initialized to a value of min(MEMORY_TARGET-PGA_AGGREGATE_TARGET, SGA_MAX_SIZE (if set by the user)) and will auto-tune subcomps.
• If neither is set, they will be auto-tuned without any minimum or default values. We will have a policy of distributing the total server memory in a fixed ratio to the the SGA and PGA during initialization. The policy is to give 60% for sga and 40% for PGA at startup.

If MEMORY_TARGET is not set or set to set to 0 explicitly (default value is 0 for 11g):

• If SGA_TARGET is set we will only auto-tune the sizes of the sub-components of the SGA. PGA will be autotuned independent of whether it is explicitly set or not. Though the whole SGA(SGA_TARGET) and the PGA(PGA_AGGREGATE_TARGET) will not be auto-tuned, i.e., will not grow or shrink automatically.
• If neither SGA_TARGET nor PGA_AGGREGATE_TARGET is set, we will follow the same policy as we have today; PGA will be auto-tuned and the SGA will not be auto-tuned and parameters for some of the sub-components will have to be set explicitly (for SGA_TARGET).
• If only MEMORY_MAX_TARGET is set, MEMORY_TARGET will default to 0 and we will not auto tune sga and pga. It will default to 10gR2 behavior within sga and pga.
• If sga_max_size is not user set, we will internally set it to MEMORY_MAX_TARGET.

In a text initialization parameter file, if you omit the line for MEMORY_MAX_TARGET and include a value for MEMORY_TARGET, the database automatically sets MEMORY_MAX_TARGET to the value of MEMORY_TARGET. If you omit the line for MEMORY_TARGET and include a value for MEMORY_MAX_TARGET, the MEMORY_TARGET parameter defaults to zero. After startup, you can then dynamically change MEMORY_TARGET to a non-zero value, provided that it does not exceed the value of MEMORY_MAX_TARGET.

If you wish to monitor the decisions made by Automatic Memory Management following views can be useful

• V$MEMORY_DYNAMIC_COMPONENTS has the current status of all memory components
• V$MEMORY_RESIZE_OPS has a circular history buffer of the last 800 SGA resize requests

3. Query for the current value of the parameter

select name, value, isdefault, isses_modifiable, issys_modifiable,

isinstance_modifiable, isdeprecated, description

from v$parameter where upper(name) = ‘V$MEMORY_DYNAMIC_COMPONENTS’;

Oracle initializatoin parameters