oracle 啟動三步驟

oracle 啟動三步驟

oracle啟動會經過三個過程，分別是nomount、mount、open

一、nomount 階段

nomount 階段，可以看到實例已經啟動。oracle進程會根據參數文件開創共享內存池。

SQL> startup nomount;
ORACLE instance started.

Total System Global Area 1653518336 bytes
Fixed Size          2213896 bytes
Variable Size         956303352 bytes
Database Buffers      687865856 bytes
Redo Buffers            7135232 bytes
SQL>

可以看到共享內存已經開辟

[root@localhost dbs]# ipcs -m

------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status      
0x00000000 98304      oracle     600        393216     2          dest         
0x00000000 131073     oracle     600        393216     2          dest         
0x00000000 163842     oracle     600        393216     2          dest         
0x00000000 196611     oracle     600        393216     2          dest         
0x00000000 229380     oracle     600        393216     2          dest         
0x00000000 262149     oracle     600        393216     2          dest         
0x00000000 294918     oracle     600        393216     2          dest         
0x00000000 327687     oracle     600        393216     2          dest         
0x00000000 360456     oracle     600        393216     2          dest         
0x33554094 1048585    oracle     660        4096       0                       
0x00000000 425994     oracle     600        393216     2          dest         
0x00000000 458763     oracle     600        393216     2          dest         
0x00000000 491532     oracle     600        393216     2          dest         
0x00000000 524301     oracle     600        393216     2          dest         
0x00000000 557070     oracle     600        393216     2          dest         
0x00000000 688143     oracle     600        393216     2          dest         
0x00000000 720912     oracle     600        393216     2          dest 

進程已經開啟

oracle     2965      1  0 04:44 ?        00:00:00 ora_pmon_test
oracle     2967      1  0 04:44 ?        00:00:00 ora_vktm_test
oracle     2971      1  0 04:44 ?        00:00:00 ora_gen0_test
oracle     2973      1  0 04:44 ?        00:00:00 ora_diag_test
oracle     2975      1  0 04:44 ?        00:00:00 ora_dbrm_test
oracle     2977      1  0 04:44 ?        00:00:00 ora_psp0_test
oracle     2979      1  0 04:44 ?        00:00:00 ora_dia0_test
oracle     2981      1  0 04:44 ?        00:00:01 ora_mman_test
oracle     2983      1  0 04:44 ?        00:00:00 ora_dbw0_test
oracle     2985      1  0 04:44 ?        00:00:00 ora_lgwr_test
oracle     2987      1  0 04:44 ?        00:00:00 ora_ckpt_test
oracle     2989      1  0 04:44 ?        00:00:00 ora_smon_test
oracle     2991      1  0 04:44 ?        00:00:00 ora_reco_test
oracle     2993      1  0 04:44 ?        00:00:00 ora_mmon_test
oracle     2995      1  0 04:44 ?        00:00:00 ora_mmnl_test
oracle     2997      1  0 04:44 ?        00:00:00 ora_d000_test
oracle     2999      1  0 04:44 ?        00:00:00 ora_s000_test

查看參數配置文件位置

SQL> show parameter spfile

NAME                     TYPE                  VALUE
------------------------------------ --------------------------------- ------------------------------
spfile                   string                /u01/app/oracle/product/11.2.4
                                       /db_1/dbs/spfiletest.ora
SQL> 

移除配置文件后startup nomount，報錯如下：

SQL> startup nomount;
ORA-01078: failure in processing system parameters
LRM-00109: could not open parameter file '/u01/app/oracle/product/11.2.4/db_1/dbs/inittest.ora'
SQL>

二、mount 階段

mount階段，oracle會根據nomount階段的參數文件來尋找控制文件的名稱和位置，一旦查找到立即鎖定該控制文件，控制文件里記錄了數據庫中的數據文件、日志文件、檢查點信息等非常重要的信息。啟動mount時，會先自動啟動nomount

startup mount

mount階段可以看到，比nomount階段多了一個database mounted的提示。

SQL> startup mount;
ORACLE instance started.

Total System Global Area 1653518336 bytes
Fixed Size          2213896 bytes
Variable Size         956303352 bytes
Database Buffers      687865856 bytes
Redo Buffers            7135232 bytes
Database mounted.
SQL> 

查看控制文件位置

SQL> show parameter control

NAME                     TYPE                  VALUE
------------------------------------ --------------------------------- ------------------------------
control_file_record_keep_time        integer                   7
control_files                string                /u01/app/oracle/oradata/test/c
                                       ontrol01.ctl, /u01/app/oracle/
                                       flash_recovery_area/test/contr
                                       ol02.ctl
control_management_pack_access       string                DIAGNOSTIC+TUNING
SQL> 

將配置文件移除，然后在啟動一次。

SQL> startup mount;
ORACLE instance started.

Total System Global Area 1653518336 bytes
Fixed Size          2213896 bytes
Variable Size         956303352 bytes
Database Buffers      687865856 bytes
Redo Buffers            7135232 bytes
ORA-00205: error in identifying control file, check alert log for more info

SQL> 

三、open階段

open階段會根據控制文件記錄的信息，定位到數據庫文件、日志文件等，正式開啟實例和數據庫之間的橋梁。如果數據文件或者日志文件缺少，那么open失敗。
open之后，如果有使用歸檔日志功能，便可看到歸檔日志的進程。

SQL> alter database open;

Database altered.

SQL> 

查看日志文件和日志文件的位置

SQL> select file_name from dba_data_files;

FILE_NAME
------------------------------------------------
/u01/app/oracle/oradata/test/users01.dbf
/u01/app/oracle/oradata/test/undotbs01.dbf
/u01/app/oracle/oradata/test/sysaux01.dbf
/u01/app/oracle/oradata/test/system01.dbf

SQL> 
SQL> select group#,member from v$logfile;

    GROUP#      MEMBER
-------------------------------------
     3          /u01/app/oracle/oradata/test/redo03.log

     2          /u01/app/oracle/oradata/test/redo02.log

     1          /u01/app/oracle/oradata/test/redo01.log

移動一個數據文件后啟動，報錯如下

SQL> startup;
ORACLE instance started.

Total System Global Area 1653518336 bytes
Fixed Size          2213896 bytes
Variable Size         956303352 bytes
Database Buffers      687865856 bytes
Redo Buffers            7135232 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 4 - see DBWR trace file
ORA-01110: data file 4: '/u01/app/oracle/oradata/test/users01.dbf'

SQL> 

如果我隨便復制一個文件進去可不可以呢？啟動如下：

SQL> alter database open;
alter database open
*
ERROR at line 1:
ORA-01122: database file 4 failed verification check
ORA-01110: data file 4: '/u01/app/oracle/oradata/test/users01.dbf'
ORA-01210: data file header is media corrupt

總結

我們可以使用statup來啟動oracle數據庫，也可以用shutdwon來關閉。如果使用startup啟動，其實已經經過了三個過程。

總的來說，沒有參數文件，實例無法創建，數據庫無法nomount成功，沒有配置文件，數據庫無法mount；沒有數據文件，數據庫無法打開使用。