Explanation of Jet Database for Windows NT 4.0

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Windows Internet Name Service (WINS) produces J<n>.log files in the%SystemRoot%\System32\Wins folder to increase the speed and efficiency ofstoring the WINS data. This article discusses these Jet files and theirpurpose.

J<n>.log Files

To increase speed and efficiency of data storage, the Jet database writescurrent transactions to log files rather than to the database directly.Therefore, the most current view of the data will be the database plus anytransactions in the log file(s). These files are also used for recovery ifthe WINS service is stopped abruptly or in an unexpected manner. If theservice is stopped in an unexpected manner, the log files willautomatically be used to re-create the correct state of the WINS database.

Log files will always be a certain size; however, they can grow quickly innumber on a very busy WINS Server. It is inevitable that WINS will writemore transactions to a log than the size of the log can accommodate. When alog file becomes filled, it is renamed to indicate that it is an older logand not in use. A new transaction log is created with the J<n>.logfilename, where <n> is a decimal number such as J50.log. The namingformat of the previous log file will be JetXXXXX.log, where each X denotesa hexadecimal number from 0 to f. Previous log files are maintained in thesame folder as the current log files.

The log files are processed (all log entries written to the database) anddeleted when a successful backup occurs or when the WINS server is shutdown gracefully. Therefore, if many J<n>.log files have accumulated,frequent backups should be scheduled to maintain the logs.

After the entries have been processed, it is possible to manually deletethe log files; however, this will prevent a successful recovery of thedatabase if it should be needed. Because of this, it is important to ensurethat the log files are not manually deleted or removed from the systemuntil a backup has been performed.

J<n>.chk Files

Jet maintains a checkpoint file, J<n>.chk, that indicates the locationwhere the last information was successfully written from the transactionlogs to the database. It is also used for recovery purposes; that is, thecheckpoint file indicates where the recovery or replaying of data shouldbegin. This checkpoint file is updated every time data is written to thedatabase file (Wins.mdb).

Res1.log and Res2.log Files

Reserved logs (Res1.log and Res2.log) are kept for emergency purposes. Morespecifically, they are used in the event that the server runs out of diskspace. If a server attempts to create another transaction log file andthere is insufficient disk space, the server will flush any outstandingtransactions into these reserved log files. The service will then shut downand log an event to the Event Viewer.

Article ID: 165915 - Last Review: 10/06/2013 23:24:12 - Revision: 1.1

Microsoft Windows NT Server 4.0 Standard Edition

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