Evaluate rows for updates

Enterprise Replication evaluates rows for replication-key updates, for WHERE-clause column updates, and for multiple updates to the same row.

The following list describes an occurrence in a transaction and the Enterprise Replication action:
  • Replication-key updates

    Enterprise Replication translates an update of the replication key into a delete of the original rows and an insert of the row images with the new replication key. If triggers are enabled on the target system, insert triggers are run.

  • WHERE-clause column updates

    If a replicate includes a WHERE clause in its data selection, the WHERE clause imposes selection criteria for rows in the replicated table.

    • If an update changes a row so that it no longer passes the selection criteria on the source, it is deleted from the target table. Enterprise Replication translates the update into a delete and sends it to the target.
    • If an update changes a row so that it passes the selection criteria on the source, it is inserted into the target table. Enterprise Replication translates the update into an insert and sends it to the target.
  • Multiple-row images in a transaction

    Enterprise Replication compresses multiple-row images and only sends the net change to the target. Because of this, triggers might not execute on the target database. For more information, see Triggers.

Enterprise Replication supports the replication of BYTE and TEXT data types (simple large objects) and BLOB and CLOB data types (smart large objects), and opaque user-defined data types, as well as all built-in Informix® data types. However, Enterprise Replication implements the replication of these types of data somewhat differently from the replication of other data types. For more information, see Replication of large objects, and Replication of opaque user-defined data types.