This hook is primarily provided for backward compatibility purposes. Unless you are using the ScriptVersion extended option you can safely perform schema changes without using this hook by using the START SYNCHRONIZATION SCHEMA CHANGE statement. See START SYNCHRONIZATION SCHEMA CHANGE statement [MobiLink].

When this hook is implemented, dbmlsync locks the tables being synchronized by default.

This stored procedure is intended for making schema changes to deployed remote databases. Using this hook for schema upgrades ensures that all changes on the remote database are synchronized before the schema is upgraded, which ensures that the database continues to synchronize. When this hook is being used you should not set the dbmlsync extended option LockTables to off.

During any synchronization where the upload was applied successfully and acknowledged by MobiLink, this hook is called after the sp_hook_dbmlsync_download_end hook and before the sp_hook_dbmlsync_end hook. This hook is not called during download-only synchronization or when a file-based download is being created or applied.

Actions performed in this hook are committed immediately after the hook completes. It is safe to commit or rollback in this hook.

• Schema changes in remote clients

The following example uses the sp_hook_dbmlsync_schema_upgrade procedure to add a column to the Dealer table on the remote database. If the upgrade is successful the sp_hook_dbmlsync_schema_upgrade hook is dropped.

CREATE PROCEDURE sp_hook_dbmlsync_schema_upgrade()
BEGIN
 -- Upgrade the schema of the Dealer table. Add a column:
 ALTER TABLE Dealer
  ADD dealer_description VARCHAR(128);

 -- Change the script version used to synchronize
 ALTER SYNCHRONIZATION SUBSCRIPTION sub1
  SET SCRIPT VERSION='v2';


 -- If the schema upgrade is successful, drop this hook:
 UPDATE #hook_dict
  SET value = 'on success'
  WHERE name = 'drop hook';
END;