Transactions and Logging

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Changes made to a database may be logged, to provide back-up protection in the event of hardware failure, provided that the changes occur within a transaction and that the databanks involved have the LOG option. Transaction handling is, therefore, important even in standalone environments where concurrency control issues do not arise.

Options

Transaction control and logging is determined at the databank level by options set when the databank is defined. The options are:

• LOG

  All operations on the databank are performed under transaction control. All transactions are logged.

• TRANSACTION

  All operations on the databank are performed under transaction control. No transactions are logged.

• WORK

  All operations on the databank are performed without transaction control (even if they are requested within a transaction), and are not logged. Sets of operations (DELETE, UPDATE or INSERT on several rows) that are interrupted will not be rolled back.

• READ ONLY

  Only read operations are allowed, i.e no UPDATE, DELETE or INSERT can be performed.

Note: All important databanks should be defined with LOG option, so that valuable data is not lost by any system failure.

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