Windows Internet Name Service (WINS) produces J<n>.log files in the
%SystemRoot%\System32\Wins folder to increase the speed and efficiency of
storing the WINS data. This article discusses these Jet files and their
To increase speed and efficiency of data storage, the Jet database writes
current transactions to log files rather than to the database directly.
Therefore, the most current view of the data will be the database plus any
transactions in the log file(s). These files are also used for recovery if
the WINS service is stopped abruptly or in an unexpected manner. If the
service is stopped in an unexpected manner, the log files will
automatically 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 in
number on a very busy WINS Server. It is inevitable that WINS will write
more transactions to a log than the size of the log can accommodate. When a
log file becomes filled, it is renamed to indicate that it is an older log
and not in use. A new transaction log is created with the J<n>.log
filename, where <n> is a decimal number such as J50.log. The naming
format of the previous log file will be JetXXXXX.log, where each X denotes
a hexadecimal number from 0 to f. Previous log files are maintained in the
same folder as the current log files.
The log files are processed (all log entries written to the database) and
deleted when a successful backup occurs or when the WINS server is shut
down 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 delete
the log files; however, this will prevent a successful recovery of the
database if it should be needed. Because of this, it is important to ensure
that the log files are not manually deleted or removed from the system
until a backup has been performed.
Jet maintains a checkpoint file, J<n>.chk, that indicates the location
where the last information was successfully written from the transaction
logs to the database. It is also used for recovery purposes; that is, the
checkpoint file indicates where the recovery or replaying of data should
begin. This checkpoint file is updated every time data is written to the
database file (Wins.mdb).
Res1.log and Res2.log Files
Reserved logs (Res1.log and Res2.log) are kept for emergency purposes. More
specifically, they are used in the event that the server runs out of disk
space. If a server attempts to create another transaction log file and
there is insufficient disk space, the server will flush any outstanding
transactions into these reserved log files. The service will then shut down
and log an event to the Event Viewer.