Databases Reference
In-Depth Information
If your database is closed, Oracle will not allow you to open it if all members of one online redo log group are
experiencing a media failure. When you attempt to open your database, you'll see a message similar to this:
ORA-00313: open failed for members of log group...
Depending on the status reported in V$LOG for the failed group, use Table
14-1
to determine what action to take.
How It Works
Your target database's alert.log file contains the best information for determining what type of failure has occurred. If
only one member of a multiplexed group fails, then you will be able to detect this only by inspecting the alert.log file.
You can also try to stop and start your database. If all members of a group have experienced media failure, then Oracle
will not let you open the database and will display an ORA-00313 error message.
The alert.log file will also tell you where additional error messages have been written to trace files:
Additional information: 3
Checker run found 1 new persistent data failures
Errors in file /u01/app/oracle/diag/rdbms/o12c/o12c/trace/o12c_lgwr_10531.trc:
When diagnosing online redo log issues, the V$LOG, V$LOGFILE, and V$LOG_HISTORY views are particularly
helpful. You can query these views while the database is mounted or open. Table
14-2
briefly describes each view.
Table 14-2.
Useful Views Related to Online Redo Logs
View
Description
V$LOG
Displays the online redo log group information stored in the control file.
V$LOGFILE
Displays online redo log file member information.
V$LOG_HISTORY
History of online redo log information in control file.
The STATUS column of the V$LOG view is particularly useful when working with online redo logs groups.
Table
14-3
describes each status and meaning for the V$LOG view.
Table 14-3.
Status for Online Redo Log Groups in the V$LOG View
Status
Meaning
CURRENT
The log group that is currently being written to by the log writer.
ACTIVE
The log group is required for crash recovery and may or may not have been archived.
CLEARING
The log group is being cleared out by an alter database clear logfile command.
CLEARING_CURRENT
The current log group is being cleared of a closed thread.
INACTIVE
The log group isn't needed for crash recovery and may or may not have been archived.
UNUSED
The log group has never been written to; it was recently created.
The STATUS column of the V$LOGFILE view also contains useful information. This view contains information
about each physical online redo log file member of a log group. Table
14-4
provides descriptions of the status of each
log file member.
