A special version of the the existing Apply Engine that reads the source datastore locally and writes records that can be loaded to the same type or even a different type of target database, using a database load utility. Often this engine can use unmodified versions of the "mapping" PROCS used by the Apply Engine and only the target datastore type will be modified to output comma separated records to one or more individual files that then are used as input to the chosen database load utility. The engine will often have to be parametrized to allow specification of the particular source descriptions (Tables, segments, records, etc). Then the parameter driven engine will be run as many times as needed to generate files for each of the specified descriptions.
If the existing Apply Engine is maintained and runs on another platform. The Unload Engine script can be maintained there as well using all the existing "parts" files. The Unload Engine can be parsed on that platform and then only the parser output, usually referred to as a .prc file can be transferred to the source platform for execution in the native operating environment.
Example
An Unload Engine configured to run as a on zOS using the <engine>.prc file created by the Parser on linux and transferred to zOS. The Engine will execute as a BMP on zOS with a parameter in the JOB that Identifies the DBD specific engine PDS member and passes the the IMS instance to the Engine at startup. It will create three "comma" delimited files, one for each SEGMENT previously selected from the DBD for the downstream application. It will also create a separate file containing a record for each SEGMENT unloaded for reconciliation purposes.
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