?在oracle11g以前的版本中,参数processes和sessiones一般是sessiones=1.1*processes+1的关系，但是在oracle11g中，参数processes和sessiones的关系好像变成了sessions=1.5*processes+26 。

下面我们来做验证:

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SYS@ats>select * from v$version;

BANNER
----------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
PL/SQL Release 11.2.0.2.0 - Production
CORE??? 11.2.0.2.0????? Production
TNS for Linux: Version 11.2.0.2.0 - Production
NLSRTL Version 11.2.0.2.0 - Production

SYS@ats>show parameter processes;

NAME???????????????????????????????? TYPE?????????????????? VALUE
------------------------------------ ---------------------- ------------------------------
aq_tm_processes????????????????????? integer??????????????? 0
db_writer_processes????????????????? integer??????????????? 1
gcs_server_processes???????????????? integer??????????????? 0
global_txn_processes???????????????? integer??????????????? 1
job_queue_processes????????????????? integer??????????????? 1000
log_archive_max_processes??????????? integer??????????????? 4
processes??????????????????????????? integer??????????????? 500
SYS@ats>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
session_cached_cursors?????????????? integer??????????????? 50
session_max_open_files?????????????? integer??????????????? 10
sessions???????????????????????????? integer??????????????? 776
shared_server_sessions?????????????? integer
SYS@ats>

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我们然后把processes改为1000 看sessions变成多少了:

SYS@ats>alter system set processes=1000 scope=spfile;

系统已更改。

SYS@ats>startup force;
ORACLE 例程已经启动。

Total System Global Area 3206836224 bytes
Fixed Size????????????????? 2230768 bytes
Variable Size??????????? 2483029520 bytes
Database Buffers????????? 704643072 bytes
Redo Buffers?????????????? 16932864 bytes
数据库装载完毕。
数据库已经打开。
SYS@ats>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???????????