There are three processes to start oracle, nomount, mount, open
I. nomount stage
During the nomount phase, you can see that the instance has started.The oracle process creates a shared memory pool based on the parameter file.
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>
You can see that shared memory has been developed
[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
The process is already started
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
View parameter profile location
SQL> show parameter spfile
NAME TYPE VALUE
------------------------------------ --------------------------------- ------------------------------
spfile string /u01/app/oracle/product/11.2.4
/db_1/dbs/spfiletest.ora
SQL> After removing the configuration file, startup nomount reported the following error:
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 stage
In mount phase, oracle looks for the name and location of the control file based on the parameter file of nomount phase. Once it finds the control file, it locks it immediately. The control file records important information such as data files, log files, checkpoint information in the database.When mount is started, nomount is automatically started first
startup mount
As you can see in the mount phase, there is one more prompt for database mounted than in the nomount phase.
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>
View Control File Location
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>
Remove the profile and start it once.
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 Phase
The open phase officially opens the bridge between the instance and the database by locating database files, log files, etc. based on the information recorded in the control file.If the data file or log file is missing, open fails.
After open, if you use the archive logging feature, you can see the progress of archiving the log.
SQL> alter database open; Database altered. SQL>
View the location of log files and log files
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
Start after moving a data file with the following error
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>
Would it be okay if I just copied a file in?Start as follows:
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
summary
We can use statup to start the oracle database or shutdwon to close it.If you start with startup, there are actually three processes involved.
In general, without parameter files, instances cannot be created, databases cannot be nomount ed successfully, databases cannot mount without configuration files, databases cannot be opened for use without data files.