COMMAREA length mismatch

COMMAREA and channel/container problems — length mismatches, missing data — break program-to-program communication.

What it means

• EIBCALEN tells the called program how much data arrived; trusting a fixed layout without checking it causes overlays.
• Channels/containers are the modern alternative with named data.

Common causes

• Caller and program disagree on COMMAREA length.
• EIBCALEN not checked before referencing the area.
• Container name misspelled or not created.
• Channel not passed on LINK/XCTL.

How to diagnose

• Display EIBCALEN at program entry.
• Compare layouts on both sides — use a shared copybook.
• Trace container puts/gets by name.

How to fix it

• Check EIBCALEN before touching the COMMAREA.
• Share one copybook between caller and callee.
• Fix container names.

Example: Validate EIBCALEN on entry

Length-check the COMMAREA before using it.

Interview tip

• Q: How would you troubleshoot a COMMAREA length mismatch in production?
• A: I would display EIBCALEN, compare both sides layouts via the shared copybook, and fix the length agreement.

Prevention checklist

• One shared copybook for each COMMAREA.
• Always validate EIBCALEN.