Database Reference
In-Depth Information
Removing a Control File
You may run into a situation in which you experience a media failure with a storage device that contains one of your
multiplexed control files:
ORA-00205: error in identifying control file, check alert log for more info
In this scenario, you still have at least one good control file. To remove a control file, follow these steps:
Identify which control file has experienced media failure by inspecting the
alert.log
for
information:
1.
ORA-00210: cannot open the specified control file
ORA-00202: control file: '/u01/dbfile/O12C/control02.ctl'
Remove the unavailable control file name from the
CONTROL_FILES
parameter. If you're
using an
init.ora
file, modify the file directly with an OS editor (such as
vi
). If you're
using an
spfile
, modify the
CONTROL_FILES
parameter with the
ALTER SYSTEM
statement.
In this
spfile
example the
control02.ctl
control file is removed from the
CONTROL_FILES
parameter:
2.
SQL> alter system set control_files='/u01/dbfile/O12C/control01.ctl'
scope=spfile;
This database now has only one control file associated with it. You should never run a
production database with just one control file. See the section “Adding a Control File,”
earlier in this chapter, for details on how to add more control files to your database.
3.
Stop and start your database:
SQL> shutdown immediate;
SQL> startup;
Managing Online Redo Logs
Online redo logs store a record of transactions that have occurred in your database. These logs serve the following
purposes:
•
Provide a mechanism for recording changes to the database so that in the event of a media
failure, you have a method of recovering transactions.
•
Ensure that in the event of total instance failure, committed transactions can be recovered
(crash recovery) even if committed data changes have not yet been written to the data files.
•
Allow administrators to inspect historical database transactions through the Oracle LogMiner
utility.
•
They are read by Oracle tools such as GoldenGate or Streams to replicate data.
You're required to have at least two online redo log groups in your database. Each online redo log group must
contain at least one online redo log member. The member is the physical file that exists on disk. You can create
multiple members in each redo log group, which is known as multiplexing your online redo log group.
