Basic Recovery Logging

To log updates to one or more files you need to create a database reference file containing the name of the file(s) for which updates are to be logged, and the name of the log file. See Database Reference File Maintenance for details on creating database reference files.

You do not need to include an extension when you specify the log file name as this is generated automatically by the Fileshare Server. If you do specify an extension, the following message is displayed:

FS180-W The log filename specified has an extension. The name of the 
log file has been changed to "filename".

During the logging process the Fileshare Server creates one or more recovery log files. The first recovery log file is called a starter log file, and subsequent log files are called continuation log files. The Fileshare Server creates a continuation log file whenever the current log file is backed up.

The current recovery log file always has an extension beginning with the character "L". A recovery log file that has been backed up has an extension beginning with the character "B". Following either of these letters is a two digit number indicating the recovery log file number, starting at 01. These automatically generated extensions indicate the order in which the log files were written, and hence the order in which they should be applied if a rollforward recovery is performed. For example, suppose you specify a log file called recover. When the Fileshare Server starts up it creates a log file called recover.L01 and logs updates in this file. If the recovery log file is backed up, the Fileshare Server renames the current log file recover.B01 and creates a new one called recover.L02. If the Fileshare Server is shut down, there would be two recovery log files: recover.B01 is called the starter log file and recover.L02 is a continuation log file. There is only ever one starter log file, but there can be any number of continuation log files.

When performing a recovery operation, the Basic Rollforward Recovery Utility processes the starter log file first and then the continuation log files in the order in which they were created.

Updates to data files that are referenced in the database reference file are logged unless you explicitly turn logging off:

Because of the caching used by some operating systems, not all of the information written to the log file is physically written to disk. The Fileshare Server periodically calls the operating system to force the log file updates to be written. By default, the log file is flushed after every 100 records are written to it. You can configure this interval using the /lc (log count) option when you add the log file name to the database reference file. If you specify a log count of zero, the Fileshare Server does not make any calls to the operating system to flush the updates to disk. Instead, the operating system controls the flushing of the log file to disk.

The log file updates are also flushed to disk after every COMMIT operation.

If a transaction was pending at the time of a system failure, the Basic Rollforward Recovery Utility implicitly rolls back the transaction when the files are recovered.