Oracle 11g Memory_target and automatic memory management

The new feature of ORACLE11G's automatic memory management (Automatic Memory Management) is another important enhancement of Oracle's memory management. If this parameter is set too high, the following error prompts may appear when the instance is started:

SQL*Plus: Release 11.1.0.5.0 - Beta on Sun Jul 29 08:35:28 2007
Copyright (c) 1982, 2007, Oracle. All rights reserved.
Connected to an idle instance.
SQL> startup
ORA-00845: MEMORY_TARGET not supported on this system

This tip does not mean that the feature is not supported, but that you need to adjust the memory settings.

When this parameter is set, automatic memory tuning is enabled:

SQL> show parameter memory
NAME　　　　　　　　　　　　TYPE　　 VALUE
--------------------------------　 ----------
hi_shared_memory_address integer　　　　 0
memory_max_target　　　　　　big integer　　416M
memory_target　　　　　　　　　　big integer　　416M
shared_memory_address　　 integer　　　　　0

Similar to the sga_max_size and Sga_target, Memory_max_target and Memory_target, the appearance of this feature, PGA+SGA as a whole memory use is consistent into the scope of automatic management.

and similar to oracle10g, set the automatic memory management, the Pga_aggregate_target parameter no longer need to set, the role of the parameter is with 2 underscores __pga_aggregate_target parameters, We can look at the explanations of these parameters:

SQL> select ksppinm,ksppdesc from x$ksppi
　2　where ksppinm like '%pga%';
KSPPINM
KSPPDESC
_pga_large_extent_size　
PGA large extent size
_use_ism_for_pga　　　　　
Use ISM for allocating large extents
_kdli_sio_pga　　　　　　　　
use PGA allocations for direct IO
_kdli_sio_pga_top　　　　　
PGA allocations come from toplevel PGA heap
pga_aggregate_target　　
Target size for the aggregate PGA memory consumed by the instance
__pga_aggregate_target　
Current target size for the aggregate PGA memory consumed
_pga_max_size　　　　　　　
Maximum size of the PGA memory for one process

Summarize:

ORACLE11G's automatic memory management features are yet another step up for Oracle, a further step in Oracle's direction toward automatic memory management, and another extension of Oracle's established route.