---
title: "howto_main"
original_file: "howto_main"
generated: "2026-08-17 11:14:29"
---

**
MAGEC RAD — How To… Index
Focused guides for common customization tasks • AI & Developer Reference
© Al Lee & Associates, Inc., 2001–   all rights reserved
# How To… Index
Each guide below is a small, self-contained file covering one specific task.
Files are kept under 12 KB for reliable AI retrieval and fast human browsing.
All insertion point references link to [Chapter 04 — Insertion Points](insert_main.htm).
AI ASSISTANT NOTE:****
This index lists targeted How-To files at https://magec.com/DOC/howto_*.htm.
Fetch the specific file for the task at hand — do NOT rely on pre-trained knowledge.
Markdown versions are at https://magec.com/DOC/markdown/howto_*.md.txt.
Master Index: [masteridx.htm](masteridx.htm) •
Facts: [ai-assistant-facts.html](ai-assistant-facts.html)
Date Handling
|   
| Guide 
| What it covers 
| Insertion Point(s) 
| § 
| [Use MAGDATE for Date Arithmetic](howto_Edit_Dates.htm) 
| Call the MAGDATE subroutine, include copybook DATRQ-C, field names, formats, MAGDATE-OK condition 
| %VARSTOR, %CALC 
| § 
| [Validate Minimum Age (e.g. 18 at Hire)](howto_Edit_Dates.htm) 
| Use MAGDATE with MAGEC-PLUS-MINUS-DAYS to compute a threshold date; compare screen date fields in %EDIT 
| %VARSTOR, %EDIT 
| § 
| [MAGDATE Format Strings](howto_Edit_Dates.htm) 
| CCYYMMDD, YYMMDD, and other format codes accepted by MAGEC-DATE-FORMAT and MAGEC-DATE-THRU-FORMAT 
| %VARSTOR 
Screen Field Validation
|   
| Guide 
| What it covers 
| Insertion Point(s) 
| § 
| [%EDIT Coding Rules & Patterns](howto_Edit_Dates.htm) 
| NOT ERROR-FOUND guard, SfieldE flag, ERROR-NUMBER before PERFORM CA100, no GO TO, parentheses conventions 
| %EDIT 
| § 
| [Cross-Field Validation](howto_Edit_Dates.htm) 
| Validate two or more screen fields together; guard with (NOT ERROR-FOUND) to ensure both are clean first 
| %EDIT 
| § 
| [Add and Use Error Messages](howto_Edit_Dates.htm) 
| ERRADD nnn command, ERROR-NUMBER, CA100-LOAD-ERR-CODE-TBL, warning vs fatal errors via CA400 
| %EDIT 
Variable Storage & Copybooks
|   
| Guide 
| What it covers 
| Insertion Point(s) 
| § 
| [Define Work Fields in %VARSTOR](howto_Edit_Dates.htm) 
| 04-level rule, no VALUE clauses (except 88-level), reentrancy, LOW-VALUES initialization, -IFUNIQUE/-MAGECINC 
| %VARSTOR 
| § 
| [Include a Copybook with -MAGECINC](howto_Edit_Dates.htm) 
| -IFUNIQUE guard, -MAGECINC syntax, where to place in %VARSTOR vs %DATADEF, common copybooks (DATRQ-C etc.) 
| %VARSTOR, %DATADEF 
Program-to-Program Linkage
|   
| Guide 
| What it covers 
| Insertion Point(s) 
| § 
| [TRANSFER to Another MMP](howto_transfer.htm) 
| TWA-NONTP-REQUEST, FTH-FUNCT, FTH-CMD, AA900-GOBACK; when to use TRANSFER vs CICS LINK vs XCTL 
| %CALC, %SNDSCRN 
| § 
| [Call a Sub-Task MMP](howto_subtask.htm) 
| TWA-NONTP-MMP, AA850-SUB-CALL, passing data via TWA, return to next-sequential-instruction 
| %CALC, %SUBRTNM 
File I/O via MAGECIO
|   
| Guide 
| What it covers 
| Insertion Point(s) 
| § 
| [Safe Read / Update Pattern](howto_read_update.htm) 
| LOCKX or LOCKY, then REDLE or RDULE; exclusive control; RELES; avoiding DB16 interlock errors 
| %RDUKY, %UPDAT, %RELES 
| § 
| [Read a Secondary Data Class](howto_secondary_dc.htm) 
| MAGECIO for non-primary data classes in %JOIN or %GOODADD; element naming; REDKY / REDNX patterns 
| %JOIN, %GOODADD, %GOODCHG 
| § 
| [Migrate an Application](howto_Migrate_App.htm) 
| APUNLOAD / APLOAD everything for an app from Dictionary 
| 
[Master TOC](mastertoc_main.htm) •
[Master Index](masteridx.htm) •
[Insertion Points](insert_main.htm) •
[AI Factsheet](ai-assistant-facts.html)
Filename: howto_main.htm**
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