ITAB_DUPLICATE_KEY — ITAB_DUPLICATE_KEY Dump Causes and Fixes

This is a catchable runtime exception, not a fatal ABAP processing error in itself, but it still terminates the program if nothing catches CX_SY_ITAB_DUPLICATE_KEY. It fires on an INSERT statement (INSERT itab, INSERT LINES OF, INSERT INITIAL LINE) or on APPEND to a table whose type enforces a unique key: HASHED TABLE, SORTED TABLE with UNIQUE KEY, or a STANDARD TABLE explicitly declared with UNIQUE KEY. The runtime checks the key of the row being inserted against existing rows and refuses the operation rather than silently overwriting or duplicating. The dump means the data feeding that insert contains two or more rows that resolve to the same key value, and the code did not anticipate that. It is a data-shape mismatch between what the table type promises (uniqueness) and what the data actually contains.

Work through the short dump top to bottom before touching code.

If the cause is genuine duplicate business data that should be summed or merged, replace the INSERT with COLLECT, or add explicit READ TABLE with key before INSERT and update the existing line instead; this is a code change requiring a transport. If the cause is a missing sy-subrc check, wrap the INSERT in a check on sy-subrc equal to 4 and handle the duplicate deliberately, either by logging it, skipping it, or updating the existing entry; also a code change under change management. If the table type itself was wrong for the data (declared unique when duplicates are valid), change the declaration to STANDARD TABLE without a unique key, or to SORTED TABLE with a non-unique key, after confirming no downstream logic relies on the uniqueness guarantee; this is a more invasive change and needs regression testing before transport. If the cause is upstream data quality in a custom table, the immediate incident fix is to deduplicate the offending rows in that table, and the durable fix is adding a proper primary key or unique secondary index at the database level, which is a functional and data-cleanup task, not purely an ABAP one.

The reflex fix is wrapping the INSERT or APPEND in TRY CATCH cx_sy_itab_duplicate_key and doing nothing in the CATCH block, or catching the broader cx_root. The dump disappears immediately and the program runs to completion, which looks like success. What actually happened is that the duplicate row was silently dropped. Downstream, that shows up as a missing line item, an incomplete total, a document that reconciles wrong, or a report that undercounts, discovered days or weeks later by someone who has no idea the itab insert ever failed, because the log shows a clean run.

Treat any INSERT or APPEND into a uniquely-keyed internal table as needing an explicit sy-subrc check or a deliberate CATCH with logging, never a silent catch. Where duplicates are expected and should be summed, use COLLECT from the start rather than INSERT. During code review, flag any HASHED or SORTED UNIQUE table declaration and ask what happens if the source data repeats the key, and require a test case with duplicate input data before the transport is released.

ABAP development owns the fix in nearly all cases, since the resolution is a code change to the insert logic or table declaration. Functional or master data teams get involved only when the root cause is duplicate records in a custom table feeding the program. The handover note should state the exact table name, its key fields, the source of the duplicate data, and whether the fix is COLLECT-based merging, a subrc check, or a table type change.

SAPSQL_ARRAY_INSERT_DUPREC is the database-level counterpart, raised when the duplicate is detected by the database rather than the ABAP runtime during an array INSERT into a DB table. ITAB_ILLEGAL_INDEX and TABLE_INVALID_INDEX are other internal-table runtime errors worth ruling out first if the short dump text is ambiguous. UNCAUGHT_EXCEPTION appears in the dump header whenever CX_SY_ITAB_DUPLICATE_KEY is not handled by any TRY CATCH in the call stack.