STEP command

The STEP command causes z/OS® Debugger to dynamically step through a program, executing one or more program statements. In full-screen mode, it provides animated execution.

STEP ends if one or more of the following conditions is reached:
  • User attention interrupt
  • A breakpoint is encountered
  • Normal or unusual termination of the program
  • a programming language or Language Environment® condition or exception
Read syntax diagramSkip visual syntax diagramSTEPinteger*INTOOVERRETURN;
integer
Indicates the number of statements performed. The default value is 1. If integer is greater than 1, the statement is performed as if it were that many repetitions of STEP with the same keyword and a count of one. The speed of execution, or the pace of stepping, is set by either the SET PACE command, or with the Pace of visual trace field on the Profile panels.
*
Specifies that the program should run until interrupted. STEP * is equivalent to GO.
INTO
Steps into any called procedures or functions. This means that stepping continues within called procedures or functions.
OVER
Steps over any procedure call or function invocations. This operand provides full-speed execution (with no animation) while in called procedures and functions, resuming STEP mode on return.

If you are debugging a disassembled program, verify that you have set a breakpoint in the calling program. Without the breakpoint, z/OS Debugger cannot resume STEP mode on return and the application continues to run until it ends.

RETURN
Steps to the return point the specified number of levels back, halting at the statement following the corresponding procedure call or function invocation. This operand provides full-speed execution (with no animation) for the remainder of the current procedure or function, and for any called procedures or functions, resuming STEP mode on return.

If you are debugging a LangX COBOL or disassembled program, do not use the STEP RETURN command because z/OS Debugger cannot identify the return point. Instead, set a breakpoint in the calling program and enter the GO command.

Usage notes

  • In the figure below, PGM A calls PGM B.
    Flowchart of program 'PGM A' calling program 'PGM B'. After program 'PGM B' is done running, program flow returns to program 'PGM A'.

    Assume that the current execution point is on PGM B and, at the line ADD 5 TO MYNUM. At this point, you decide you don't need to see any more of the code in PGM B. By issuing STEP RETURN on the command line, z/OS Debugger returns to the first line of code after the CALL command that called PGM B, as indicated by the arrow. You can then continue stepping through PGM A.

  • If STEP is specified in a command list (for example, as the subject of an IF command or WHEN clause), all subsequent commands in the list are ignored.
  • If STEP is specified within the body of a loop, it causes the execution of the loop to end.
  • To suppress the logging of STEP commands, use the SET ECHO command.
  • If two operands are given, they can be specified in either order.
  • The animation execution timing is set by the SET PACE command.
  • The source panel provides a means of suppressing the display of selected listings or files. This gives some control of "debugging scope," because animated execution does not occur within a load module where the source listing or source file is not displayed.
  • If you are debugging a disassembled program and attempt to step out of the current CU, a message appears. The message informs you to set a breakpoint outside the current CU. Without that breakpoint, z/OS Debugger cannot stop the application. After you have set the breakpoint, you can resume running your application by entering a z/OS Debugger command like STEP or GO.
  • If you are debugging a program that does not use the standard linkage conventions for R13, R14, and R15, and you enter the STEP RETURN or the STEP command on a statement that returns to a higher level CU, z/OS Debugger does not stop at the expected instruction in the higher-level CU.
  • When PLAYBACK ENABLE is in effect, you can use the STEP command to move forward or backward one or more statements. You cannot use the INTO, OVER, and RETURN keywords. Each STEP command moves forward or backward the number of statements specified or implied by the integer parameter.
  • If the DATA option of the PLAYBACK ENABLE command is in effect, you can access program variables after each STEP command.
  • You can use the STEP command in remote debug mode by entering it in the Debug Console or the Action field, which is in the Optional Parameters section of the Add a Breakpoint task.
  • With Enterprise COBOL V5 (and later), STEP OVER, an out-of-line PERFORM, behaves the same as it does when stepping over a called subroutine. However, you cannot use STEP RETURN from within the out-of-line PERFORM to return to the statement after the PERFORM.

Examples

  • Step through the next 25 statements and if an application subroutine or function is called, continue stepping into that subroutine or function. 
    STEP 25 INTO;
  • Step through the next 25 statements, but if any application subroutines or functions are called, switch to full-speed execution without animation until the subroutine or function returns. 
    STEP 25 OVER;
  • Return at full speed through three levels of calls. 
    STEP 3 RETURN;