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CDC-6003 Schema mismatch

Code: CDC-6003 (SCHEMA_MISMATCH). Raised at task start. Not retried.

What the connector observed​

The schema topic holds a version of a captured table whose columns, key or supplemental logging differ from the data dictionary, and the table's last DDL is not later than the position the task resumes from. A DDL within ten seconds of the resume point counts as later, because the time of an SCN is known only to within a few seconds. The message names the table, the stored version and both times.

Why it stopped rather than continued​

The connector decodes rows with the version the schema topic recorded. A difference that no DDL ahead in the redo explains means a DDL was not captured: for example, the offset was moved forward past it, the table was outside the include pattern when it changed, or the schema topic belongs to another database or connector. Decoding with either layout could publish values under the wrong columns.

Confirm the cause​

SELECT owner, object_name, last_ddl_time FROM dba_objects
WHERE owner = :owner AND object_name = :table AND object_type = 'TABLE';
SELECT SCN_TO_TIMESTAMP(:resume_scn) FROM dual;

Recover​

  • If the redo from before the DDL is still available, stop the connector and move its offset back before the DDL (moving the offset by hand), then resume. The DDL is mined again and becomes a version. Commits already delivered are skipped as long as the last_commit_* fields are kept.

  • If the schema topic belongs to another connector or database, point cdc.schema.topic at the right topic, then restart.

  • If the change is understood and the records published since the DDL are acceptable, clear the table's entry: with the connector stopped, produce a tombstone (a record with a null value) for the table's key on the schema topic, then resume. The table then starts again from the dictionary's current layout. Copy the key exactly as it is stored, for example with kcat:

    kcat -C -b "$BROKERS" -t cdc.cdc.schema -e -f '%k\n' | sort -u     # find the table's key
    printf '%s|\n' "$KEY" | kcat -P -b "$BROKERS" -t cdc.cdc.schema -K '|' -Z

    The key holds the server (the topic prefix), the PDB, the owner and the table. Reload the table with a snapshot signal if consumers need its rows in the new layout.

Restart a failed task with:

curl -s -X POST "$CONNECT/connectors/$NAME/restart?includeTasks=true&onlyFailed=true"