Implementing conflict resolution

This section describes what you need to do to implement custom conflict resolution in SQL Remote.

SQL Remote allows you to define conflict resolution triggers to handle UPDATE conflicts. Conflict resolution triggers are fired only at a consolidated database, when messages are applied by a remote user. When an UPDATE conflict is detected at a consolidated database, the following sequence of events takes place.

  1. Any conflict resolution triggers defined for the operation are fired.
  2. The UPDATE takes place.
  3. Any actions of the trigger, as well as the UPDATE, are replicated to all remote databases, including the sender of the message that triggered the conflict.

    In general, SQL Remote for SQL Anywhere does not replicate the actions of triggers: the trigger is assumed to be present at the remote database. Conflict resolution triggers are fired only at consolidated databases, and so their actions are replicated to remote databases.

  4. At remote databases, no RESOLVE UPDATE triggers are fired when a message from a consolidated database contains an UPDATE conflict.
  5. The UPDATE is carried out at the remote databases.

At the end of the process, the data is consistent throughout the setup.

UPDATE conflicts cannot happen where data is shared for reading, but each row (as identified by its primary key) is updated at only one site. They only occur when data is being updated at more than one site.

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