Adding Transaction Processing

Adding transaction processing to an application permits complex, atomic updates and automatic recovery in the case of software or hardware failures. Transaction processing can be added with the transaction processing sub-API or with SetOperationState().

To add efficient transaction processing, use the transaction processing sub-API described in “Data Integrity”. If your application is already prepared for multi-user use, replacing LockISAM(ctENABLE) calls with Begin(ctTRNLOG | ctENABLE) and replacing LockISAM(ctFREE) calls with Commit(ctFREE) or Abort(ctFREE) calls, depending on the status of the transaction at that point, is a simple method of implementing transaction processing. See ctixmg.c for an example and “Data Integrity” for more details.

To add transaction processing quickly, though not in the most efficient manner, use SetOperationState() with the OPS_AUTOISAM_TRN mode. This performs a transaction around each ISAM update. See “SetOperationState” for more details. This method does not effectively lock updates. You will still need to use some form of locking control. Consider the OPS_LOCKON_GET mode for SetOperationState() to minimize network traffic.

Once the application supports transaction processing, add either of the transaction processing file modes, ctTRNLOG or ctPREIMG, to the data files requiring transaction processing using the UpdateFileMode() function. Index files must be rebuilt to add or remove transaction processing. For additional information on Transaction Processing, please see “Data Integrity”.