Customizing File Manager to use an I/O exit

File Manager allows you to provide a user I/O exit for use when processing data. This enables you to process records in data sets which are subject to any kind of pre- or post-processing not offered directly by File Manager. Such processing could include compression, encryption, or other site-specific activities performed on records in a data set.

There are a number of ways that data sets can be processed, and how the processing is made visible to users. Therefore File Manager allows you to provide an I/O exit, to be associated with a particular data set, and to specify the name of the exit. The I/O exit is a program that interfaces with File Manager using a predefined communication area.

This I/O exit is not intended to fully support compressed or encrypted data sets. Specifically, it does not provide member name list access to data sets which are in other than PDS or PDSE format. However, you can access members of a proprietary compressed library (PDS or other format) through the I/O exit, as long as the member name is known and is provided to File Manager.

The File Manager I/O exit operates only on the data, not the data set, and supports the following functions:
  • Interactive view, edit and browse in the File Manager base component
  • Batch and interactive utilities:
    • Data set copy (DSC)
    • Data set compare (DSM)
    • Data set edit in batch (DSEB)
    • Data set generate (DSG)
    • Data set print (DSP)
    • Data set update (DSU)
    • Find/change (FCH)

You cannot use the File Manager I/O exit to operate directly on COBOL copybook or PL/I include data sets, or on template data sets. The I/O exit, when specified, can apply only to the data being processed, not to the template or copybook data sets used to format or select the processed data. However, the I/O exit can be used when the template or copybook data set is itself the subject of a function.

You use the library management system (LMS) exit to process COBOL copybook or PL/I include data sets, or template data sets, when associated with an input or output data set. For information on providing an LMS exit, see Customizing File Manager to use library management system libraries and The library management system exit.

To specify that an I/O exit can be used, set the USEIOX option, in FMN0POPT. If required, you can also provide the name of a site-specific I/O exit. For more information about USEIOX, see USEIOX. For information about changing the options in FMN0POPT, see Changing the default options. This exit name can be overridden by the user interactively or in batch. File Manager for z/OS User’s Guide and Reference describes how to use the I/O exit.