Applies to
TIB_Transaction

Declaration
Property RecVersion : boolean;

Description
This property only takes affect when Isolation is set to tiCommitted. It determines if the most recent record version must be seen or if an earlier record version can be seen in order to avoid a deadlock when reading records.

Setting this property to true will avoid deadlocks by allowing uncommitted changes in the database to be ignored. Only the most recent committed changes will be visible. I consider this the "friendly" mode of committed isolation.

If the most recent record must be seen and another user or transaction has an update or delete pending then a deadlock condition is generated when the record that has been updated or deleted is encountered. Deadlock will occur even when selecting the data using this mode of tiCommitted isolation. Unless LockWait is true an immediate Deadlock cannot be avoided. Which, in this case, would prevent a user from finishing the processing of the query.

When RecVersion is set to false LockWait is generally set to true so that queries or multi-record updates, deletes, etc. will be able to process to completion without a deadlock exception. It is VERY important that all transactions performing updates, deletes, etc. have a very short duration in this type of configuration so that a client application will not appear to be locked up indefinitly.

This is the only case where a deadlock can be hit when selecting data other than if there is a conflict with another transaction that was started using tiConsistency against the same table. tiConsistency is effectively a way to force exclusive access to specified tables during a transaction.