1 先看oracle的監(jiān)聽(tīng)和oracle的服務(wù)是否都啟動(dòng)了,。啟動(dòng)oracle監(jiān)聽(tīng)：
cmd的命令行窗口下,，輸入lsnrctl start,，回車即啟動(dòng)監(jiān)聽(tīng),。

2 查看oracle的sid叫什么,，比如創(chuàng)建數(shù)據(jù)庫(kù)的時(shí)候，實(shí)例名叫“abc”,，那么先手工設(shè)置一下oralce的sid,，cmd命令窗口中，set ORACLE_SID=abc

3 再輸入sqlplus  /nolog,回車
再輸入 conn / as sysdba;回車

4 再輸入startup,，回車.這步是啟動(dòng)oracle服務(wù),。如果startup啟動(dòng)被告知已經(jīng)啟動(dòng)了，可以先輸入shutdown immediate,；等shutdown結(jié)束之后,，再輸入startup。

5 過(guò)幾秒鐘等命令運(yùn)行完成,，就能連接了,。這個(gè)時(shí)候，可以輸入"select * from user_tables;"測(cè)試一下,，看是否有查詢結(jié)果,。

6 出現(xiàn)ORA-01034和ORA-27101的原因是多方面的：主要是oracle當(dāng)前的服務(wù)不可用，shared memory realm does not exist,，是因?yàn)閛racle沒(méi)有啟動(dòng)或沒(méi)有正常啟動(dòng),，共享內(nèi)存并沒(méi)有分配給當(dāng)前實(shí)例.所以，通過(guò)設(shè)置實(shí)例名,，再用操作系統(tǒng)身份驗(yàn)證的方式,，啟動(dòng)數(shù)據(jù)庫(kù)。這樣數(shù)據(jù)庫(kù)就正常啟動(dòng)了,，就不會(huì)報(bào)ORA-01034和ORA-27101兩個(gè)啟動(dòng)異常了,。
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今天在測(cè)試庫(kù)上遇到了ORA-27101的錯(cuò)誤，當(dāng)通過(guò)客戶端連接到db時(shí)返回如下：

[oracle@bluerin admin]$ sqlplus system/oracle@test

SQL*Plus: Release 11.1.0.6.0 - Production on Tue Aug 10 11:05:04 2010

Copyright (c) 1982, 2007, Oracle.  All rights reserved.

ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Linux-x86_64 Error: 2: No such file or directory
Process ID: 0
Session ID: 0 Serial number: 0

對(duì)于這個(gè)問(wèn)題第一印象,，可能會(huì)覺(jué)得沒(méi)有足夠的內(nèi)存空間,，來(lái)創(chuàng)建共享內(nèi)存段

1.首先檢查內(nèi)核參數(shù)設(shè)置以及alert.log 文件

fs.file-max = 6553600
kernel.shmall = 2097152
kernel.shmmax = 2147483648
kernel.shmmni = 4096
kernel.sem = 250 32000 100 128
net.ipv4.ip_local_port_range = 9000 65500
net.core.rmem_default = 4194304
net.core.rmem_max = 4194304
net.core.wmem_default = 262144
net.core.wmem_max = 1048576

查看后都沒(méi)有問(wèn)題，主機(jī)有足夠的內(nèi)存,，數(shù)據(jù)庫(kù)也已經(jīng)在啟動(dòng)狀態(tài)：

SQL> select open_mode from v$database;

OPEN_MODE
----------
READ WRITE

2.之后發(fā)現(xiàn)在報(bào)錯(cuò)之后,，繼續(xù)輸入用戶名和密碼確可以登陸

Enter user-name: system
Enter password:

Connected to:
Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL>

3.查看sqlnet.log日志

[oracle@bluerin log]$ pwd
/u01/app/product/11.1.0/db_1/network/log
[oracle@bluerin log]$ cat sqlnet.log
Directory does not exist for read/write [/u01/app/product/11.1.0/db_1/log] [/u01/app/product/11.1.0/db_1/log/diag/clients]

***********************************************************************
Fatal NI connect error 12541, connecting to:
 (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=10.201.1.134)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=Oracle8)(CID=(PROGRAM=java@localhost)(HOST=localhost)(USER=oracle))))

  VERSION INFORMATION:
        TNS for Linux: Version 11.1.0.6.0 - Production
        TCP/IP NT Protocol Adapter for Linux: Version 11.1.0.6.0 - Production
  Time: 05-AUG-2010 18:30:51
  Tracing not turned on.
  Tns error struct:
    ns main err code: 12541
    TNS-12541: TNS:no listener
    ns secondary err code: 12560
    nt main err code: 511
    TNS-00511: No listener
    nt secondary err code: 111
    nt OS err code: 0

***********************************************************************

提示找不到listener......

4.檢查listener是否配置正確

[oracle@bluerin alert]$ cat /u01/app/product/11.1.0/db_1/network/admin/listener.ora
# listener.ora Network Configuration File: /u01/app/product/11.1.0/db_1//network/admin/listener.ora
# Generated by Oracle configuration tools.

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (ORACLE_HOME = /u01/app/product/11.1.0/db_1)
      (SID_NAME = siebtest)
    )
  )

LISTENER =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 10.201.1.134)(PORT = 1521))
  )

[oracle@bluerin ~]$ tnsping test

Used parameter files:
/u01/app/product/11.1.0/db_1/network/admin/sqlnet.ora

Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = 10.201.1.134)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = siebtest)))
OK (0 msec)

listener 配置沒(méi)有問(wèn)題。,。,。

5.由于實(shí)例已經(jīng)在啟動(dòng)的狀態(tài)，這時(shí)候考慮到實(shí)例注冊(cè)的問(wèn)題

SQL> show parameter local_listener

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
local_listener                       string

發(fā)現(xiàn)local_listener沒(méi)有值,。,。。。,。

6.設(shè)置local_listener參數(shù)

SQL> alter system set local_listener='(ADDRESS =(PROTOCOL=TCP)(HOST=10.201.1.134)(PORT=1521)(SID=siebtest))';

System altered.

SQL> alter system register;

System altered.

7.再次登陸成功

[oracle@bluerin alert]$ sqlplus system/oracle@test

SQL*Plus: Release 11.1.0.6.0 - Production on Tue Aug 10 12:51:11 2010

Copyright (c) 1982, 2007, Oracle.  All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL>

 總結(jié)：

    如果LOCAL_LISTENER丟失,，會(huì)導(dǎo)致自動(dòng)實(shí)例注冊(cè)失敗，數(shù)據(jù)庫(kù)實(shí)例不會(huì)識(shí)別Listener,當(dāng)Listener連接

數(shù)據(jù)庫(kù)實(shí)例的時(shí)候,，由于Listener沒(méi)有注冊(cè),，導(dǎo)致了 ORA-27101: shared memory realm does not exist.