ORACLE推导参数Derived Parameter介绍

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

aq_tm_processes                      integer     0

db_writer_processes                  integer     1

gcs_server_processes                 integer     0

job_queue_processes                  integer     10

log_archive_max_processes            integer     10

processes                            integer     870

SQL> show parameter session;

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

java_max_sessionspace_size           integer     0

java_soft_sessionspace_limit         integer     0

license_max_sessions                 integer     0

license_sessions_warning             integer     0

logmnr_max_persistent_sessions       integer     1

session_cached_cursors               integer     400

session_max_open_files               integer     10

sessions                             integer     962

shared_server_sessions               integer

SQL> select ceil(870*1.1) +5 from dual;

CEIL(870*1.1)+5

---------------

            962

同时修改参数sessions和processes，然后重启数据库，然后检查参数processes与sessions的关系。

SQL> alter system set sessions=800 scope=spfile;

System altered.

SQL> alter system set processes=600 scope=spfile;                    

System altered.

SQL> shutdown immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup;

ORACLE instance started.

Total System Global Area 1509949440 bytes

Fixed Size                  2096472 bytes

Variable Size            1358955176 bytes

Database Buffers          100663296 bytes

Redo Buffers               48234496 bytes

Database mounted.

Database opened.

SQL> show parameter processes;

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

aq_tm_processes                      integer     0

db_writer_processes                  integer     1

gcs_server_processes                 integer     0

job_queue_processes                  integer     10

log_archive_max_processes            integer     10

processes                            integer     600

SQL> show parameter session

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

java_max_sessionspace_size           integer     0

java_soft_sessionspace_limit         integer     0

license_max_sessions                 integer     0

license_sessions_warning             integer     0

logmnr_max_persistent_sessions       integer     1

session_cached_cursors               integer     400

session_max_open_files               integer     10

sessions                             integer     800

shared_server_sessions               integer

SQL> select ceil(1.1*600)+5 from dual;

CEIL(1.1*600)+5

---------------

            665

如上所示，processes与sessions的关系已经不成立了：sessions=(1.1 * processes) + 5（Oracle 10g）。主要还是因为推导参数session设置后，覆盖了推导值。这个参数值已经写入了参数文件spfile或pfile当中。

SQL> create pfile=‘/u01/app/oracle/product/10.2.0/db_1/dbs/init_session.ora‘ from spfile;

File created.

SQL> 

[oracle@DB-Server dbs]$ grep session init_session.ora

*.session_cached_cursors=400

*.sessions=800

[oracle@DB-Server dbs]$ grep process init_session.ora

*.job_queue_processes=10

*.log_archive_max_processes=10

*.processes=600

参考资料：

http://www.dba-oracle.com/t_derived_parameters.htm

ORACLE推导参数Derived Parameter介绍

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