Using REXX under TSO/ISPF

Objectives
On successful completion of this course, attendees will be able to:

• describe the concepts, facilities and structure of the TSO REXX language
• write and debug REXX programs executing in the TSO environment
• make effective use of TSO supplied commands from within REXX programs to further enhance TSO facilities.

Who Should Attend
Systems programmers, operations analysts, senior operators, operations support staff and application programmers who will be writing and/or maintaining TSO REXX programs.

Duration
3 days

Course Code
RT

Contents
Introduction to TSO REXX
Executing REXX EXECs; elements of the REXX language: Clauses, Tokens, Labels, Assignments, Instructions and Commands; constant and variable symbols; Simple, Compound & Stem variable symbols; operators for concatenation, arithmetic, comparison & logical operations.
This segment introduces the terminology associated with REXX and shows how data fields are defined and initialised.

Tracing and debugging
Using TRACE instruction for debugging; using immediate commands HI, HT, TS and TE; use of EXECUTIL; interpreting TRACE output.
This segment describes the tracing facilities available in REXX to enable more rapid problem determination.

Parsing strings
Parsing variables and strings; basic parsing techniques; special templates; place holders, literal patterns and numeric patterns.
Explains how input from any source can be split into useable entities using various techniques.

Control instructions
Decisions: IF, THEN, ELSE, SELECT, WHEN, OTHERWISE; creating and controlling loops: DO WHILE, UNTIL, FOREVER, LEAVE, ITERATE; introduction to sub-routines.
This segment describes the IF, THEN, ELSE logic used in REXX.

Sub-routines and functions
Internal and external sub-routines; how to create internal and external functions; passing arguments and results to and from sub-routines and functions; CALL; RETURN; EXIT; PROCEDURE; RESULT.
This segment shows how to create subroutines and functions, and identifies the difference between them

REXX built in functions
Introduction to REXX supplied built in functions; how to use the most useful ones: ARG, DATE, TIME, DATATYPE, LENGTH, POS, WORDS, LEFT, RIGHT, STRIP, SPACE, COPIES and WORD.
This segment explains the commonly used REXX built-in functions, and indicates their use in REXX programs.

Data stack management
LIFO and FIFO stacking; avoiding the stack; writing to the stack: PUSH and QUEUE; reading from the stack: PARSE PULL; creating and managing extensions to the stack: MAKEBUF, QBUF and DROPBUF; interrogating the stack: QUEUE, QELEM; creating and managing private stacks: NEWSTACK, DELSTACK and QSTACK.
This segment describes the stack mechanisms used by TSO and REXX.

Using TSO commands & functions
Using TSO commands and functions: SYSDSN, LISTDSI, MSG, OUTTRAP, PROMPT and SYSVAR; reading and writing datasets with EXECIO.
Shows how to invoke and use TSO commands from a REXX program.