Release 10.1A: OpenEdge Getting Started:
Installation and Configuration

> ## Managing the OpenEdge event log file size

> The event log (`LG`) file expands as you use the database. If it becomes too large, you can use the `PROLOG` utility, in either an offline or online mode, to reduce the event log file’s size. Using the `PROLOG` utility, you can:

> - Truncate log entries offline — To remove old log entries. To remove log entries from an `LG` file, use the OpenEdge Log Maintenance (`PROLOG`) utility or a text editor. The syntax to use the `PROLOG` utility in the offline mode is presented in the "Remove old log entries" section.
> - Truncate log file entries online — To remove entries in the database log file while the database is online. The online activity is intended to help you avoid bringing the database down and restarting it after the database has been truncated. Using this approach, the need to shutdown the database to archive the log file is eliminated. However, keep in mind that it is possible to lose some messages while performing this procedure due to the nature of the real-time processing. The syntax to use the `PROLOG` utility in the online mode is presented in the "Truncate the database log file" section.
> Caution: During the time in which the multi-stepped online truncation process occurs, some messages written to the log file might because the database is neither quiet nor latched/locked to prevent writes.

> ##### Remove old log entries

> This section describes topics related to removing and truncating log file entries.

> | To remove old log entries from an event log file, enter the following command:

>     prolog database-name

> The `PROLOG` utility removes all but the most recent entries from the log file. For more information, see the details about `PROLOG` in the "Truncate the database log file" section and in OpenEdge Data Management: Database Administration .

> ##### Truncate the database log file

> The purpose of this activity is to allow you to truncate a database log file that exists and the file’s size is greater than 3072 bytes.

> ##### Truncating a log file online

> The online activity is intended to help you avoid bringing the database down and restarting it after the database has been truncated; the need to shutdown the database to archive the log file is eliminated. An online truncation log file records the start and end of truncation activities and records errors to indicate when a truncation failed, as shown:

>     prolog database-name [-online]

> `prolog`

> Enables truncation of a log file. By default, a log file is truncated offline.

> ``database-name``

> The name of the database to be truncated.

> `-online`

> Using the option `-online`, you do not have to shutdown and restart the database to truncate the database log file.

> The online truncation option copies the last 3072+ bytes to a buffer, truncates the file, and then copies the buffer to the file.

> Note: Keep in mind that if the `-online` option is used, the `prolog` command can truncate a log file even if the database is in use.

> For more information about the syntax associated with these online and offline activities, see OpenEdge Data Management: Database Administration .

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