Transaction Processing

Transaction processing enables you to group a set of data file updates together into one logical unit of work, known as a transaction. The changes you make as part of a transaction can be:

A transaction can include multiple updates to multiple data files on multiple Fileshare Servers.

A transaction starts when your program performs the first update operation (WRITE, REWRITE or DELETE) on a file which has the WITH ROLLBACK clause defined in its SELECT statement after:

A transaction terminates when:

Notes:

  • The COMMIT and ROLLBACK verbs release all the record locks held by a program on every data file. This does not depend on whether or not you specified the WITH ROLLBACK clause for a particular file.
  • The time taken to process a COMMIT or ROLLBACK operation is directly proportional to the number of updates performed in that transaction.
  • If you try to CLOSE a file that is participating in an active transaction, a 9/100 error status is returned and the file remains open. A COMMIT or ROLLBACK needs to be issued before the CLOSE can be executed.
  • When you use the WITH ROLLBACK clause, multiple record locking is implicitly defined on the file.

Before using transaction processing you are strongly advised to do the following to ensure the highest level of integrity for your data:

Record locks are implicitly obtained on every record that is updated in a transaction. If a transaction is temporarily suspended, for example, if your program requests input and the user is not responding, record locks can remain in the file for a considerable length of time. If another Fileshare Client tries to access the locked records, and a specified length of time has passed, the Fileshare Server aborts (rolls back) the transaction. When this happens, the transaction is said to be timed out by the Fileshare Server. See the section Automatic Record Lock Timeout for further information.

Note:

By keeping the number of updates performed in a transaction to a minimum, the number of record locks obtained is also kept to a minimum. This reduces the number of record locking conflicts between Fileshare Clients sharing the data, and increases the speed of any subsequent COMMIT or ROLLBACK operations.