Store and Forward

The Store and Forward feature is available for supported databases. This feature lets you write records for Alarm Logging and Point Logging to storage files whenever the Database Logger loses its connection to the database.

When the Database Logger successfully reconnects to the database and Store and Forward is enabled when the Database Logger starts, the Database Logger checks for stored data files (that is, .SQL files) in the storage directory. If it finds files, it generates a DB_START_FORWARD alarm then checks the files for stored data. If there is no stored data in the files, the Database Logger logs the following message to the Status Log:

No forward data found in <store_path>

and clears the DB_START_FORWARD alarm.

If there is data to forward, the Database Logger goes through each file and forwards the data to the database. When all the data has been forwarded, or if the Database Logger loses its connection to the database, it clears the DB_START_FORWARD alarm and stops processing the storage files.

$image\Note.gif$ Note: Stored data and new logged data are sent in parallel to the database, and all Maintenance actions are ignored while data is being stored.

After a file is forwarded to the database, the Database Logger sends the following message to the Status Log:

Forward: <file_name> succ: <no_suc> fail <no_fail>

If there are failures, the following message will also be logged:

Forward: See log <filename> for errors.

If the Database Logger cannot process a SQL statement in a storage file, it generates a log file with the same name as the storage file and the extension .LOG. The log file contains the statement forwarded to the database and the error message returned by the database.

If the Database Logger encounters no problems when forwarding data, no .LOG file is generated.

$image\Note.gif$ Note: If you have Store and Forward enabled and storage files exist when you shut down the Database Logger and you then disable Store and Forward, the Database Logger will not forward records from the storage files when it restarts.

You can open a storage file and examine its contents in, for example, Notepad.

Important: Store and Forward is supported only for local Microsoft Access databases, not remote Access databases.

More information

$image\Buttongraysm.png$	Store and forward enabled.
$image\Buttongraysm.png$	Store and forward file names.
$image\Buttongraysm.png$	How maximum number of records works.
$image\Buttongraysm.png$	Procedure to change directory and record defaults.
$image\Buttongraysm.png$	Database-disconnect-recovery.