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Schema changes

TwinCommit detects schema changes on replicated tables; it does not propagate them automatically. When a table’s definition changes in a way the log cannot describe, TwinCommit marks that one table as broken and keeps replicating every other table.

Operations that mark a table broken

Section titled “Operations that mark a table broken”
  • ALTER TABLE that adds, drops or alters columns
  • Bulk loads that are not logged (for example Db2 LOAD, or NOT LOGGED INITIALLY)
  • Turning off change capture on the table (DATA CAPTURE NONE on Db2, dropping supplemental logging on Oracle)
  • DROP TABLE

Operations that need no action

Section titled “Operations that need no action”
  • TRUNCATE, which is replicated as a truncate on the target
  • Index changes, statistics collection and REORG
  • Adding or dropping constraints that do not change columns

Applying a column change

Section titled “Applying a column change”
  1. Stop twincommit run.
  2. Change the target table to match, or drop it and let twincommit ddl -apply recreate it.
  3. Re-snapshot the table:
    Terminal window
    twincommit snapshot -config pipeline.yaml -tables SALES.ORDERS
  4. Start twincommit run again.