Input/Output routine

The input/output (I/O) replaceable routine is also called the read input/write output data routine. The system calls the I/O routine to:

Read a record from a specified DD
Write a record to a specified DD
Open a DD

The DD must be allocated to either a sequential data set or a single member of a partitioned data set. The name of the system-supplied I/O routine is IRXINOUT.

Note:

The system supplied I/O routine does not support I/O on files allocated to data sets with spanned, track overflow, or undefined record formats.
To permit FORTRAN programs to call IRXINOUT, TSO/E provides an alternate entry point for the IRXINOUT routine. The alternate entry point name is IRXIO.

If a read is requested, the routine returns a pointer to the record that was read and the length of the record. If a write is requested, the caller provides a pointer to the record to be written and the length of the record. If an open is requested, the routine opens the file if the file is not yet open. The routine also returns a pointer to an area in storage containing information about the file. You can use the IRXDSIB mapping macro to map this area. The mapping macro is in SYS1.MACLIB.

You specify the name of the I/O routine in the IOROUT field in the module name table. Module name table describes the format of the module name table. I/O processing is based on the QSAM access method.

The I/O routine is called for:

Initialization. When IRXINIT initializes a language processor environment, the system calls the I/O replaceable routine to initialize I/O processing.
Open, when:
- You use the LINESIZE built-in function in an exec
- Before the language processor does any output
For input, when:
- A PULL or a PARSE PULL instruction is processed, and the data stack is empty, and the language processor environment is not integrated into TSO/E (see Types of environments - integrated and not integrated into TSO/E).
- A PARSE EXTERNAL instruction is processed in a language processor environment that is not integrated into TSO/E (see Types of environments - integrated and not integrated into TSO/E).
- The EXECIO command is processed.
- A program outside of REXX calls the I/O replaceable routine for input of a record.
For output, when:
- A SAY instruction is processed in a language processor environment that is not integrated into TSO/E (see Types of environments - integrated and not integrated into TSO/E).
- Error messages must be written.
- Trace (interactive debug facility) messages must be written.
- A program outside of REXX calls the I/O replaceable routine for output of a record.
Termination. When the system terminates a language processor environment, the I/O replaceable routine is called to cleanup I/O.