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Oracle Monitoring Redo Log Status

Chapter 6 Oracle Tablespace and File Internals Scripts

Monitoring Redo Log Status

Redo log status should be monitored to determine which logs are in use and whether there are any odd status codes, such as stale log indications or indications of corrupt redo logs. The log files can have the following status values:

  • USED. Indicates either that a log has just been added (never used), or that a RESETLOGS command has been issued.
     

  • CURRENT. Indicates a valid log that is in use.
     

  • ACTIVE. Indicates a valid log file that is not currently in use.
     

  • CLEARING. Indicates a log is being re-created as an empty log due to DBA action.
     

  • CLEARING CURRENT. Means that a current log is being cleared of a closed thread. If a log stays in this status, it could indicate there is some failure in the log switch.
     

  • INACTIVE. Means that the log is no longer needed for instance recovery but may be needed for media recovery.

The v$logfile table has a status indicator that gives these additional codes:

  • INVALID. File is inaccessible.
     

  • STALE. File contents are incomplete (such as when an instance is shut down with SHUTDOWN ABORT or due to a system crash).
     

  • DELETED. File is no longer used.

The script below provides some basic information on log status. The listing shows an example of output from the log_stat.sql script.

log_stat.sql

COLUMN first_change# FORMAT 99999999  HEADING Change#
COLUMN group#        FORMAT 9,999     HEADING Grp#
COLUMN thread#       FORMAT 999       HEADING Th#
COLUMN sequence#     FORMAT 999,999   HEADING Seq#
COLUMN members       FORMAT 999       HEADING Mem
COLUMN archived      FORMAT a4        HEADING Arc?
COLUMN first_time    FORMAT a21       HEADING 'Switch|Time'
 
BREAK ON thread#
SET PAGES 60 LINES 131 FEEDBACK OFF
ttitle 'Current Redo Log Status'
SPOOL log_stat
 
SELECT
   thread#,
   group#,
   sequence#,
   bytes,
   members,
   archived,
   status,
   first_change#,
   TO_CHAR(first_time, 'DD-MM-YYYY HH24:MI:SS') first_time
FROM
 

    sys.v_$log
ORDER BY
    thread#,
    group#;
 
SPOOL OFF
PAUSE Press Enter to continue
SET PAGES 22 LINES 80 FEEDBACK ON
CLEAR BREAKS
CLEAR COLUMNS
TTILE OFF

Here is a sample listing:
                                                   Switch                 
                                                         
Th# Grp#  Seq#     BYTES Mem Arc? STATUS   Change# Time
--- ---- -----   ------- -------- -------- ------- ------------------
  1    1 4,489   1048576   2 NO   INACTIVE  719114 15-JUN-97 16:54:23
       2 4,490   1048576   2 NO   INACTIVE  719117 15-JUN-97 16:56:10
       3 4,491   1048576   2 NO   CURRENT   719120 15-JUN-97 17:02:22


 



 

The Oracle script collection contains more than 600 working Oracle scripts.  You can download them immediately at this link:
 


 

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