Oracle MTS模式下 进程地址与会话信息

前几天在客户现场，检查一个数据库时发现在OS上根本没有明确的数据库连接，但是在数据库内部却可以看到会话信息。
想了一会，才明白过来，原来这是一个MTS系统，共享服务器模式已经很久没有遇到了，几乎忘却了。

在检查会话信息时，你会发现，用户进程的进程地址PADDR是相同的，都是812960DC ：

SQL> select paddr,sid,username,osuser,process,terminal,machine,logon_time from v$session;

PADDR    SID USERNAME   OSUSER     PROCESS      TERMINAL        MACHINE           LOGON_TIME
-------- --- ---------- ---------- ------------ --------------- ----------------- -------------------
8129301C   1            oracle     6568         UNKNOWN         EYGLEORACLE1      2010-09-27 11:39:07
812933DC   2            oracle     6570         UNKNOWN         EYGLEORACLE1      2010-09-27 11:39:08
8129379C   3            oracle     6573         UNKNOWN         EYGLEORACLE1      2010-09-27 11:39:08
81293B5C   4            oracle     6576         UNKNOWN         EYGLEORACLE1      2010-09-27 11:39:11
81293F1C   5            oracle     6578         UNKNOWN         EYGLEORACLE1      2010-09-27 11:39:11
812942DC   7            oracle     6580         UNKNOWN         EYGLEORACLE1      2010-09-27 11:39:11
8129469C   9            oracle     6582         UNKNOWN         EYGLEORACLE1      2010-09-27 11:39:11
81294A5C  10            oracle     6584         UNKNOWN         EYGLEORACLE1      2010-09-27 11:39:11
81294E1C  11            oracle     6586         UNKNOWN         EYGLEORACLE1      2010-09-27 11:39:11
812951DC  12            oracle     6588         UNKNOWN         EYGLEORACLE1      2010-09-27 11:39:11
8129559C  13            oracle     6590         UNKNOWN         EYGLEORACLE1      2010-09-27 11:39:11
8129595C  14            oracle     6592         UNKNOWN         EYGLEORACLE1      2010-09-27 11:39:11
812960DC  15 EYGLE      eyg        3572:220     EYGLEE          EYGLEENMO\\EYGLEE  2010-10-28 09:04:14
812960DC  16 EYGLE      eyg        1804:3708    EYGLEE          EYGLEENMO\\EYGLEE  2010-10-28 09:04:19
8129685C  17            oracle     6611         UNKNOWN         EYGLEORACLE1      2010-09-27 11:39:13
81295D1C  20 EYGLE      root                    unknown         EYGLEWEB1         2010-10-28 07:45:30
812960DC  24 EYGLE      root                    unknown         EYGLEWEB1         2010-10-28 09:11:13
812960DC  30 EYGLE      eyg        3296:2968    EYGLEE          EYGLEENMO\\EYGLEE  2010-10-28 09:04:22
812960DC  31 EYGLE      root                    unknown         EYGLEWEB1         2010-10-28 08:21:09
812960DC  32 EYGLE      root                    unknown         EYGLEWEB1         2010-10-28 09:13:45
812960DC  33 EYGLE      oracle     721122                       oracle2           2010-10-13 13:34:13
8129649C  35 SYS        oracle     23221        pts/1           EYGLEORACLE1      2010-10-28 09:24:21

而 812960DC  进程正是Dispatcher进程 oracle@EYGLEORACLE1 (D000)

SQL> select addr,spid,program from v$process;

ADDR     SPID         PROGRAM
-------- ------------ ------------------------------------------------
81292C5C              PSEUDO
8129301C 6568         oracle@EYGLEORACLE1 (PMON)
812933DC 6570         oracle@EYGLEORACLE1 (DIAG)
8129379C 6573         oracle@EYGLEORACLE1 (LMON)
81293B5C 6576         oracle@EYGLEORACLE1 (LMD0)
81293F1C 6578         oracle@EYGLEORACLE1 (LMS0)
812942DC 6580         oracle@EYGLEORACLE1 (LMS1)
8129469C 6582         oracle@EYGLEORACLE1 (DBW0)
81294A5C 6584         oracle@EYGLEORACLE1 (LGWR)
81294E1C 6586         oracle@EYGLEORACLE1 (CKPT)
812951DC 6588         oracle@EYGLEORACLE1 (SMON)

ADDR     SPID         PROGRAM
-------- ------------ ------------------------------------------------
8129559C 6590         oracle@EYGLEORACLE1 (RECO)
8129595C 6592         oracle@EYGLEORACLE1 (CJQ0)
81295D1C 6594         oracle@EYGLEORACLE1 (S000)
812960DC 6596         oracle@EYGLEORACLE1 (D000)
8129649C 23222        oracle@EYGLEORACLE1 (TNS V1-V3)
8129685C 6611         oracle@EYGLEORACLE1 (LCK0)
81296FDC 9955         oracle@EYGLEORACLE1 (S003)

而通过监听器也可以看到，数据库所有的连接都来自Dispatcher，没有Dedicated模式的连接建立：

[oracle@EYGLEORACLE1 log]$ lsnrctl service

LSNRCTL for Linux: Version 9.2.0.7.0 - Production on 28-OCT-2010 09:38:51

Copyright (c) 1991, 2002, Oracle Corporation.  All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=jgzx1)(PORT=1521)))
Services Summary...
Service "PLSExtProc" has 1 instance(s).
  Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...
    Handler(s):
      "DEDICATED" established:0 refused:0
         LOCAL SERVER
Service "jgzx" has 2 instance(s).
  Instance "jgzx1", status READY, has 3 handler(s) for this service...
    Handler(s):
      "DEDICATED" established:0 refused:0 state:ready
         REMOTE SERVER
         (ADDRESS=(PROTOCOL=TCP)(HOST=jgzx1)(PORT=1521))
      "DEDICATED" established:0 refused:0 state:ready
         LOCAL SERVER
      "D000" established:117664 refused:0 current:21 max:1002 state:ready
         DISPATCHER <machine: EYGLEORACLE1, pid: 6596>
         (ADDRESS=(PROTOCOL=tcp)(HOST=jgzx1)(PORT=32812))
  Instance "jgzx2", status READY, has 2 handler(s) for this service...
    Handler(s):
      "DEDICATED" established:0 refused:0 state:ready
         REMOTE SERVER
         (ADDRESS=(PROTOCOL=TCP)(HOST=jgzx2)(PORT=1521))
      "D000" established:114273 refused:0 current:18 max:1002 state:ready
         DISPATCHER <machine: EYGLEORACLE2, pid: 5563>
         (ADDRESS=(PROTOCOL=tcp)(HOST=jgzx2)(PORT=32784))
Service "jgzx1" has 1 instance(s).
  Instance "jgzx1", status UNKNOWN, has 1 handler(s) for this service...
    Handler(s):
      "DEDICATED" established:0 refused:0
         LOCAL SERVER
The command completed successfully

由此，MTS模式的特点显而易见，其减少进程可以缩减系统的资源消耗，但是显然会导致排队，并不适用于对响应时间要求较高的OLTP系统。