Transactions in the synchronization process

The MobiLink server incorporates changes uploaded from each MobiLink client into the consolidated database in one transaction. It commits these changes once it has completed inserting new rows, deleting old rows, making updates, and resolving any conflicts.

The MobiLink server prepares the blocking download, including all deletes, inserts, and updates, using another transaction. If you specify download acknowledgement and the client confirms a successful download, the MobiLink server commits the download transaction. If the application encounters problems or cannot reply when blocking download acknowledgement is specified, the MobiLink server instead rolls back the download transaction. The default is to not use download acknowledgement.

Caution

There should be no implicit or explicit commit or rollback in your SQL synchronization scripts or the procedures or triggers that are called from your SQL synchronization scripts. COMMIT or ROLLBACK statements within SQL scripts alter the transactional nature of the synchronization steps. If you use them, MobiLink cannot guarantee the integrity of your data in the event of a failure.

Tracking downloaded information

MobiLink uses a last download timestamp, stored in the remote database, to help simplify how downloads are created.

The primary role of the download transaction is to select rows in the consolidated database. If the download fails, the remote uploads the same last download timestamp over again, and no data is lost.

See Using last download times in scripts.

Begin and end transactions

The MobiLink client processes information in the download in one transaction. Rows are inserted, updated, and deleted to bring the remote database up to date with the consolidated data.

The MobiLink server uses two other transactions, one at the beginning of synchronization and one at the end. These transactions allow you to record information regarding each synchronization and its duration. Thus, you can record statistics about attempted synchronizations, successful synchronizations, and the duration of synchronizations. Since data is committed at various points in the process, these transactions also let you commit data that can be useful when analyzing failed synchronization attempts.