Content of the Oracle Control File

1. functions and features of Control Files
 
1) define the current physical status of the database
2) maintain data consistency: If the checkpoints in the control file are consistent with those in the data file, the data is consistent and can be started to the open state)
How to view Data Consistency:
SQL> select file #, checkpoint_change # from v $ datafile; [read from control file]
FILE # CHECKPOINT_CHANGE #
----------------------------
1 172373
2 172373
3 172373
4 172373
SQL> select file #, checkpoint_change # from v $ datafile_header; [read from the data file header]
FILE # CHECKPOINT_CHANGE #
----------------------------
1 172373
2 172373
3 172373
4 172373
3) binary files
4) read in the mount phase
5) record Backup Recovery Information
 
2. Control File Content
 
The control file mainly records the following information:
(1) Database Name
(2) Data File name and location
(3) redo log name and location
(4) tablespace name
(5) Current Log serial number
(6) checkpoint Information
(7) log history information
(8) RMAN Information
Where:
MAXLOGFILES: used to specify the maximum number of log groups for an Oracle database
MAXLOGMEMBERS: used to specify the maximum number of logs in each log group.
MAXDATAFILES: used to specify the maximum number of data files in an Oracle database
MAXINSTANCES: used to specify the maximum number of routines that can access the database at the same time
MAXLOGHISTORY: used to specify the maximum number of logs that can be recorded in a control file.
When RMAN is used for backup, The RMAN backup information is recorded in the control file. The initialization parameter control_file_record_keep_time specifies the retention time of RMAN backup information in the control file. The default value is 7.
 
3. View Control Files
 
View the 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
View control file members:
SQL> select name from v $ controlfile;
NAME
-------------------------------------------------------------------------
/U01/app/oracle/oradata/test/control01.ctl