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Customizing File Manager
Customizing File Manager to use an I/O exit
Using the I/O exit control block
The I/O exit control block is a single parameter that is passed with each call from File Manager to the I/O exit and returns data from the I/O exit to File Manager.
Function codes and the flow of I/O exit processing

Customizing File Manager
- Preparing to customize File Manager
- Customizing the operating environment for File Manager
- Customizing File Manager
- Customizing the File Manager security environment
  File Manager provides security for system-oriented functions through ®either RACF (or an equivalent security product) or the FMNSECUR exit.
- Customizing File Manager to write audit records to SMF
- Customizing the File Manager audit facility for the File Manager Base component
- Customizing File Manager for national languages
  You can customize File Manager for national languages other than English.
- Customizing File Manager Service Provider for z/OS® Connect
  File Manager Service Provider for IBM® z/OS® Connect Enterprise Edition enables client applications to access IBM Z data sources using z/OS Connect.
- Customizing File Manager to use library management system libraries
- Customizing File Manager to use the Optim™ Data Privacy Provider API
- Customizing File Manager to use an I/O exit
  - Exit protocol
  - Writing your exit
  - Exit control block data names
  - Using the I/O exit control block
    The I/O exit control block is a single parameter that is passed with each call from File Manager to the I/O exit and returns data from the I/O exit to File Manager.
  - Installing your exit
- Customizing File Manager to use a scrambling exit
- Verifying the customization of File Manager
  After you have completed the initial installation and customization of File Manager Base function, you can perform the following steps to verify your customization.

Function codes and the flow of I/O exit processing

The I/O exit control block contains a function code field. This is set by File Manager before the I/O exit is called. It indicates the type of I/O function being performed by File Manager. The I/O exit is given the opportunity to perform actions at the points named by the function codes during File Manager processing. The function codes are also discussed in Exit protocol. They are: Initialization, Termination, Open, Close, Read and Write.

Note that File Manager makes the "real" I/O calls to the operating system. As a result, the I/O exit does not get control at exactly the time of the real I/O operation. Instead, the I/O exit gets control, as follows:

Open: After the "real" data set open
Close: Before the "real" close
Read: Immediately after a read from DASD (before File Manager truncation or padding or other changes)
Write: Immediately before a write to DASD (after File Manager truncation or padding or other changes)

The Function Code is the key input that your I/O exit should use to determine what actions to take. The following sections discuss the flow of control and data during I/O exit processing by focussing on the call type, as determined by the function code.