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PREIMG Transaction Files

The PREIMG (“pre-image”) transaction mode supports transaction atomicity but not transaction recoverability. PREIMG files may be updated only within an active transaction. The server stores PREIMG file updates in memory known as ‘preimage space’ until the transaction is committed or aborted. This use of preimage space guarantees atomicity and isolation of transaction operations: changes are made on an all or nothing basis and other clients do not see changes until the transaction is committed.