1、nomout阶段,该阶段启动的前提是有参数文件,若没有参数文件,系统无法启动,在该过程中,系统分配内存、开启后台进程,同时更新alter日志文件
实例nomount之前的状态:
--无实例进程
[oracle@secdb1 admin]$ echo $ORACLE_SID
PROD
[oracle@secdb1 admin]$ ps -ef|grep PROD
oracle 14890 6310 0 21:12 pts/1 00:00:00 grep PROD
--alter日志信息
[oracle@secdb1 bdump]$ ls -lrt
total 48
-rw-r----- 1 oracle oinstall 1113 Mar 4 23:15 prod_lgwr_7319.trc
-rw-r----- 1 oracle oinstall 779 Mar 5 19:42 prod_mmnl_7329.trc
-rw-r--r-- 1 oracle oinstall 40910 Mar 5 21:08 alert_PROD.log
此时启动实例到nomount状态
[oracle@secdb1 admin]$ sqlplus / as sysdba SQL*Plus: Release 10.2.0.1.0 - Production on Wed Mar 5 21:15:50 2014 Copyright (c) 1982, 2005, Oracle. All rights reserved. Connected to an idle instance. SQL> startup nomount ORACLE instance started. Total System Global Area 314572800 bytes Fixed Size 1219184 bytes Variable Size 100664720 bytes Database Buffers 209715200 bytes Redo Buffers 2973696 bytes SQL> |
此时查看进程和日志信息
[oracle@secdb1 bdump]$ ls -lrt total 52 -rw-r----- 1 oracle oinstall 1113 Mar 4 23:15 prod_lgwr_7319.trc -rw-r----- 1 oracle oinstall 779 Mar 5 19:42 prod_mmnl_7329.trc -rw-r--r-- 1 oracle oinstall 42513 Mar 5 21:15 alert_PROD.log ----------------日志文件已经更新 [oracle@secdb1 bdump]$ ps -ef|grep PROD ----------------------------系统中出现后台进程 oracle 14946 1 0 21:15 ? 00:00:00 ora_pmon_PROD oracle 14948 1 0 21:15 ? 00:00:00 ora_psp0_PROD oracle 14950 1 0 21:15 ? 00:00:00 ora_mman_PROD oracle 14952 1 0 21:15 ? 00:00:00 ora_dbw0_PROD oracle 14954 1 0 21:15 ? 00:00:00 ora_lgwr_PROD oracle 14956 1 0 21:15 ? 00:00:00 ora_ckpt_PROD oracle 14958 1 0 21:15 ? 00:00:00 ora_smon_PROD oracle 14960 1 0 21:15 ? 00:00:00 ora_reco_PROD oracle 14962 1 0 21:15 ? 00:00:00 ora_mmon_PROD oracle 14964 1 0 21:15 ? 00:00:00 ora_mmnl_PROD oracle 14965 14942 0 21:15 ? 00:00:00 oraclePROD (DESCRIPTION=(LOCAL=YES)(ADDRESS=(PROTOCOL=beq))) oracle 14988 5989 0 21:17 pts/3 00:00:00 grep PROD |
如果在$ORACLE_HOME/dbs目录下无参数文件,启动实例是现象如下:
[oracle@secdb1 dbs]$ sqlplus / as sysdba
SQL*Plus: Release 10.2.0.1.0 - Production on Wed Mar 5 21:21:19 2014
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to an idle instance.
SQL> startup nomount
ORA-01078: failure in processing system parameters
LRM-00109: could not open parameter file '/u01/app/oracle/product/10.2.0/db_1/dbs/initPROD.ora'
SQL> quit
参数寻找的优先级 spfileSID.ora----initSID.ora
在该阶段,可以进行数据库的创建、控制文件的创建
2、mount,在该阶段,启动条件是需要有控制文件,如果控制文件丢失或者损坏,启动将会报错。此时系统会打开控制文件、检查数据文件、日志文件的名称和位置,
但此时不检查文件到底是否存在不存在
mount之前:
SQL> select * from v$controlfile; no rows selected SQL> select * from v$datafile; select * from v$datafile * ERROR at line 1: ORA-01507: database not mounted mount之后 SQL> alter database mount; Database altered. SQL> select name from v$controlfile; NAME -------------------------------------------------------------------------------- /u01/app/oracle/oradata/PROD/disk1/control01.ctl /u01/app/oracle/oradata/PROD/disk2/control02.ctl SQL> select file#,name from v$datafile; FILE# name -------------------------------------------------------------------------------- 1 /u01/app/oracle/oradata/PROD/disk1/system01.dbf 2 /u01/app/oracle/oradata/PROD/disk1/undotbs01.dbf 3 /u01/app/oracle/oradata/PROD/disk1/sysaux01.dbf |
在该阶段,可以进行数据库的完全恢复、修改数据库的归档模式、移动和重命令数据文件
SQL> archive log list ---查看数据库归档模式 Database log mode No Archive Mode Automatic archival Disabled Archive destination /u01/app/oracle/product/10.2.0/db_1/dbs/arch Oldest online log sequence 3 Current log sequence 5 SQL> alter database archivelog; ---修改成归档模式 SQL> alter database noarchivelog;---修改成非归档模式 |
如果控制文件丢失,系统报错,现象如下:
SQL> startup mount ORACLE instance started. Total System Global Area 314572800 bytes Fixed Size 1219184 bytes Variable Size 100664720 bytes Database Buffers 209715200 bytes Redo Buffers 2973696 bytes ORA-00205: error in identifying control file, check alert log for more info |
3、open阶段,该阶段主要是打开数据文件、日志文件,在打开的过程中对数据文件和日志文件进行一致性检查,如果不一致,则SMON进程继续实例恢复,如果文件丢失,打开失败。
SQL> alter database open; Database altered. --如何数据文件丢下,打开失败 SQL> startup mount; ORACLE instance started. Total System Global Area 314572800 bytes Fixed Size 1219184 bytes Variable Size 79693200 bytes Database Buffers 230686720 bytes Redo Buffers 2973696 bytes Database mounted. SQL> alter database open; alter database open * ERROR at line 1: ORA-01157: cannot identify/lock data file 1 - see DBWR trace file ORA-01110: data file 1: '/u01/app/oracle/oradata/PROD/disk1/system01.dbf' |
4、小结
启动时分成三个步骤,1、nomount阶段,该阶段是实例启动,根据参数文件进行系统分配内存,启动后台进程。mount阶段,根据控制文件来进行数据文件和日志文件的名称和位置检查,把实例和数据库连接起来。open阶段,就是数据库打开阶段,打开是就需要检查文件是否正常,有没有发生文件丢失或者不一致的情况,丢失则报错,不一致则进行实例恢复。