Controlling the Logging Process

• The user of the :LOG command does not have OP capabilities or the operator has not done an :ALLOW of the :LOG command for the user.

• START was specified instead of RESTART for a file which already has records in it.

• STOP was requested while user processes are accessing the logfile.

Logging to DISC

When logging to DISC, for User Logging to continue when a full logfile is encountered, the :CHANGELOG command may be used. The :CHANGELOG command will open a new User Logging file with the same attributes as the previous file. To use the :CHANGELOG command, the User Logging filename specified in the :GETLOG command must end with the three digits "001". Each time a new logfile is constructed, by the CHANGELOG command, the value represented by the last three digits is incremented by 1 (for example, filename001 ---> filename002). If the logfile name specified with the :GETLOG command does not end with the three digits "001", a warning will be given (to the user issuing the command) that the :CHANGELOG command will not be allowed for this file.

If the ;AUTO option is specified with the :GETLOG or :ALTLOG command for a disc file, where :CHANGELOG is allowed, the User Logging process will automatically perform a :CHANGELOG whenever the disc file becomes full. If the ;AUTO option is not specified, when the disc logfile becomes full the User Logging process will close the logfile and terminate, preventing any applications which are linked to it from writing any additional log records.

Logging to TAPE

When logging to tape, if an end-of-tape is encountered, the Operator will be requested to mount the next tape in the volume set and the logging will continue. The user may issue a :CHANGELOG command for logging to be switched to a new logfile (DISC or TAPE) before end-of-tape is reached.

	NOTE: The ;AUTO option is ignored if the logfile media is TAPE.

Linking Logfiles

When a :CHANGELOG command is issued, information about the new logfile and is written to the old logfile, and information about the old logfile is written as the first record in the new logfile. This allows the recovery programs to find the next logfile in the set.

	NOTE: Using :CHANGELOG is recommended over stopping the process, switching logfiles (by renaming files or using :ALTLOG to point to a new logfile), and starting the process. Using :CHANGELOG is easier and it creates these links for use in recovery.

It is not required that all logfiles in a set be on the same media. The first file could be on disc, the second on tape, the third on disc, etc. This can be controlled with the ;DEV= option of the :CHANGELOG command.

After a System Backup

Usually, when it is time to backup a database, the operator will stop the logging processes; the database and all associated logfiles will be stored off, and the old logfile(s) will be purged from disc and rebuilt. If :CHANGELOG was allowed, it is important to use the :ALTLOG command to reset the last three digits of the logfile name back to "001". Failure to do this will cause problems when recovering data.

Obtaining Status of Open User Logging Files

To display the status information of currently open User Logging files, use the :SHOWLOGSTATUS command:

:SHOWLOGSTATUS KATHY



LOGID  CHANGE AUTO USERS STATE    CUR REC  MAX REC  % USED  



KATHY  YES    YES  1     INACTIVE  65       1023     6 %    

	NOTE: INACTIVE is displayed when a process is waiting for information from the user processes.

If there are processes with the logfile open, and a :LOG command with the STOP option is issued, the operator will receive a warning at the System Console, and the logging process will continue.