Handling Rollback Operations

A resource manager, a transactional client, or KTM can roll back a transaction if it determines that the transaction must not be committed (typically because an error has been detected).

To roll back a transaction, a resource manager can call ZwRollbackEnlistment. After the resource manager has called ZwCreateEnlistment to enlist in a transaction, it can roll back the transaction at any time before it calls ZwPrepareComplete.

Transactional clients can roll back their transactions by calling ZwRollbackTransaction. After a transactional client has called ZwCreateTransaction to create a transaction, it can roll back the transaction at any time before it calls ZwCommitTransaction.

In addition, a transactional client can set a time-out value for a transaction by calling ZwSetInformationTransaction. KTM rolls back the transaction if it has not been committed by the specified amount of time.

When a call to ZwRollbackEnlistment or ZwRollbackTransaction is made, or when a time-out value is exceeded, KTM sends a TRANSACTION_NOTIFY_ROLLBACK notification to all resource managers.

When each resource manager receives a TRANSACTION_NOTIFY_ROLLBACK notification, it must do the following:

1. Restore the transaction's data to the state that it was in before the resource manager enlisted in the transaction.

   Typically, a resource manager restores the transaction's data by copying the transaction's saved initial data from the log stream to the database's public, permanent storage. For more information about how to use log streams, see Using Log Streams with KTM.

2. Call ZwRollbackComplete.

After calling ZwRollbackComplete, the resource manager should call ZwClose to close the enlistment handle.

If a resource manager initiated the rollback operation, it must use its client interface to inform the client that the transaction failed.