一.官网说明
1.1 processes
11gR2 的文档：
Property
Description
Parameter type
Integer
Default value
100
Modifiable
No
Range of values
6 to operating system dependent
Basic
Yes
Oracle RAC
Multiple instances can have different values.
PROCESSES specifies the maximum numberof operating system user processes that can simultaneously connect to Oracle.Its value should allow for all background processes such as locks, job queueprocesses, and parallel execution processes.
The defaultvalues of the SESSIONS and TRANSACTIONS parameters arederived from this parameter. Therefore, if you change the valueof PROCESSES, you should eva luate whether to adjust the values of thosederived parameters.
http://download.oracle.com/docs/cd/E11882_01/server.112/e25513/initparams198.htm#REFRN10175
1.2 sessions
11gR1:
http://download.oracle.com/docs/cd/B28359_01/server.111/b28320/initparams220.htm#REFRN10197
Property
Description
Parameter type
Integer
Default value
Derived: (1.1 * PROCESSES) + 5
Modifiable
No
Range of values
1 to 231
Basic
Yes
11gR2
Property
Description
Parameter type
Integer
Default value
Derived: (1.5 * PROCESSES) + 22
Modifiable
No
Range of values
1 to 231
Basic
Yes
这里要注意的是到了11gR2里，sessions 的默认值计算方式变了。 该值的计算是针对dedicate 模式的。
SESSIONS specifies the maximum number of sessions that can becreated in the system. Because every login requires a session, this parametereffectively determines the maximum number of concurrent users in the system.You should always set this parameter explicitly to a value equivalent to yourestimate of the maximum number of concurrent users, plus the number ofbackground processes, plus approximately 10% for recursive sessions.
Oracle uses thedefault value of this parameter as its minimum. Values between 1 and thedefault do not trigger errors, but Oracle ignores them and uses the defaultinstead.
The defaultvalues of the ENQUEUE_RESOURCES and TRANSACTIONS parametersare derived from SESSIONS. Therefore, if you increase the valueof SESSIONS, you should consider whether to adjust the valuesof ENQUEUE_RESOURCES and TRANSACTIONS as well. (Notethat ENQUEUE_RESOURCES is obsolete as of Oracle Database 10g release2 (10.2).)
In a shared server environment, the value of PROCESSES canbe quite small. Therefore, Oracle recommends that youadjust the value of SESSIONS to approximately 1.1 * total numberof connections.
1.3 transactions
11gR2
http://download.oracle.com/docs/cd/E11882_01/server.112/e25513/initparams258.htm#REFRN10222
Property
Description
Parameter type
Integer
Default value
Derived: (1.1 * SESSIONS)
Modifiable
No
Range of values
4 to 232
Oracle RAC
Multiple instances can have different values.
TRANSACTIONS specifieshow many rollback segments to onlinewhen UNDO_MANAGEMENT = MANUAL. The maximum number of concurrenttransactions is now restricted by undo tablespace size(UNDO_MANAGEMENT = AUTO) or the number of online rollback segments(UNDO_MANAGEMENT = MANUAL).
二. 测试
2.1 测试DB版本
SQL> select * from v$version;
BANNER
-----------------------------------------------------------------------
Oracle Database 11g Enterprise EditionRelease 11.2.0.1.0 - Production
PL/SQL Release 11.2.0.1.0 - Production
CORE 11.2.0.1.0 Production
TNS for 32-bit Windows: Version 11.2.0.1.0- Production
NLSRTL Version 11.2.