Easytrieve AFTER-SCREEN

SCREEN Activity Event Flow

INITIATION PROC once at SCREEN activity entry—open files, ACCESS database, set defaults. Screen cycle repeats: BEFORE-SCREEN maps outgoing fields, runtime displays screen, operator edits, AFTER-SCREEN validates and acts. TERMINATION PROC cleanup at activity end. Multiple screens in one activity chain via GOTO or CASE navigation after AFTER-SCREEN sets next screen id field.

AFTER-SCREEN Validation Pattern

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AFTER-SCREEN. PROC
   IF ACCT-NO EQ SPACES
      ERR-MSG = 'Account required'
      GOTO SAME-SCREEN
   END-IF
   IF NOT NUMERIC(ACCT-NO)
      ERR-MSG = 'Account must be numeric'
      GOTO SAME-SCREEN
   END-IF
   PERFORM READ-MASTER
   IF NOT-FOUND EQ Y
      ERR-MSG = 'Account not found'
      GOTO SAME-SCREEN
   END-IF
   PERFORM SHOW-DETAIL-SCREEN
END-PROC

BEFORE-SCREEN Versus AFTER-SCREEN

BEFORE-SCREEN loads customer name from file into display field before operator sees screen. AFTER-SCREEN reads operator-entered account number after keypress—cannot validate empty account in BEFORE-SCREEN before operator had chance to type unless clearing prior session residue. Error message field ERR-MSG set in AFTER-SCREEN displays on redisplay via BEFORE-SCREEN on next cycle.

File Updates in AFTER-SCREEN

Approved adjustment: AFTER-SCREEN validates amount range, READ hold record, ADD amount to balance, WRITE or REWRITE per file type, commit if database. Failed validation skips update and redisplays screen with ERR-MSG. Use same FILE definitions as batch Library—online and batch share data dictionary when designed well.

EXECUTE JOB From AFTER-SCREEN

Operator approves report: AFTER-SCREEN sets parms and EXECUTE JOB PRINT-PAYROLL activity batch side generates spool. Operator sees confirmation message. Long-running JOB may async per site—message should set expectations. JCL for EXECUTE must exist in runtime environment documented for SCREEN.

Variable Lifetime on SCREEN

W working storage RESET at SCREEN activity start per variable lifetime rules. Session flags persist across screen cycles within activity unless cleared in AFTER-SCREEN. S fields may carry forward through multiple EXECUTE calls—document semantics for maintainers.

Contrast With Report AFTER-LINE

Report AFTER-LINE hooks printed detail rows in batch report writer. Screen AFTER-SCREEN hooks terminal interaction cycles—completely different runtime. Names parallel BEFORE/AFTER pattern but contexts do not interchange.

Common AFTER-SCREEN Mistakes

• Validating input in BEFORE-SCREEN before operator entry.
• PERFORM AFTER-SCREEN from JOB activity.
• Missing error path redisplay—operator sees blank screen.
• UPDATE without READ lock or concurrent update check.
• Long batch EXECUTE blocking terminal without message.
• Screen PROC placed before SCREEN executable statements incorrectly.

Explain It Like I'm Five

The screen is a form the operator fills out. BEFORE-SCREEN puts the blank form on the desk with today's date filled in. AFTER-SCREEN is the teacher collecting the form and checking answers—if something wrong, hand form back with red marks; if right, file it and show next form.

Exercises

1. Write AFTER-SCREEN check for blank required field.
2. Explain ERR-MSG flow across AFTER and BEFORE cycles.
3. Describe EXECUTE JOB use case from online approval.
4. List four screen PROC names in activity order.
5. Contrast AFTER-SCREEN with AFTER-LINE context.