oracle 启动三步骤

oracle 启动三步骤

oracle启动会通过三个过程，分别是nomount、mount、open

1、nomount 阶段

nomount 阶段，能够看到实例已经启动。oracle进程会根据参数文件开创共享内存池。

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>

能够看到共享内存已经开辟

[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

进程已经开启

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

查看参数配置文件位置

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，报错以下：

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>

2、mount 阶段

mount阶段，oracle会根据nomount阶段的参数文件来寻找控制文件的名称和位置，一旦查找到当即锁定该控制文件，控制文件里记录了数据库中的数据文件、日志文件、检查点信息等很是重要的信息。启动mount时，会先自动启动nomount

startup mount

mount阶段能够看到，比nomount阶段多了一个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>

将配置文件移除，而后在启动一次。

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>

3、open阶段

open阶段会根据控制文件记录的信息，定位到数据库文件、日志文件等，正式开启实例和数据库之间的桥梁。若是数据文件或者日志文件缺乏，那么open失败。
open以后，若是有使用归档日志功能，即可看到归档日志的进程。

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

移动一个数据文件后启动，报错以下

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>

若是我随便复制一个文件进去可不能够呢？启动以下：

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

总结

咱们可使用statup来启动oracle数据库，也能够用shutdwon来关闭。若是使用startup启动，其实已经通过了三个过程。

总的来讲，没有参数文件，实例没法建立，数据库没法nomount成功，没有配置文件，数据库没法mount；没有数据文件，数据库没法打开使用。