JetTruncateLog Function

Article
08/26/2021

Applies to: Windows | Windows Server

JetTruncateLog Function

The JetTruncateLog function is used during a backup that is initiated by JetBeginExternalBackup to delete any transaction log files that will no longer be needed once the current backup completes successfully.

    JET_ERR JET_API JetTruncateLog(void);

Parameters

This function has no parameters.

Return Value

This function returns the JET_ERR datatype with one of the following return codes. For more information about the possible ESE errors, see Extensible Storage Engine Errors and Error Handling Parameters.

Return code	Description
JET_errSuccess	The operation completed successfully.
JET_errBackupAbortByServer	The operation failed because the current external backup has been aborted by a call to JetStopBackup. Windows Server 2003: This return value is introduced in Windows Server 2003.
JET_errClientRequestToStopJetService	The operation cannot complete because all activity on the instance that is associated with the session has ceased as a result of a call to JetStopService.
JET_errInstanceUnavailable	The operation cannot complete because the instance that is associated with the session has encountered a fatal error that requires that access to all data be revoked to protect the integrity of that data. Windows XP: This return value is introduced in Windows XP.
JET_errInvalidBackupSequence	The backup operation failed because it was called out of sequence. JetTruncateLog will return this error if there are any outstanding file handles that were created using JetOpenFile for the instance.
JET_errInvalidParameter	One of the parameters that was provided contained an unexpected value, or the combination of several parameters yielded an unexpected result. This can happen for JetTruncateLog when the specified instance handle is invalid. Windows XP: This return value is introduced in Windows XP.
JET_errNoBackup	The operation failed because no external backup is in progress.
JET_errNotInitialized	The operation cannot complete because the instance that is associated with the session has not yet been initialized.
JET_errRestoreInProgress	The operation cannot complete because a restore operation is in progress on the instance that is associated with the session.
JET_errRunningInMultiInstanceMode	The operation failed because an attempt was made to use the engine in legacy mode (Windows 2000 compatibility mode) where only one instance is supported, when in fact multiple instances already exist.
JET_errTermInProgress	The operation cannot complete because the instance that is associated with the session is being shut down.

If this function succeeds, the set of transaction log files that will no longer be needed once the current backup completes successfully are deleted. The backup state machine will be advanced such that the backup of database files is no longer allowed. Only database patch files and transaction log files are permitted to be opened for backup beyond this point.

If this function fails, the backup state machine can be advanced such that the backup of database files is no longer allowed. Some number of transaction log files might be deleted that is less than the desired number, but they will always be deleted from oldest to youngest.

Requirements

Requirement	Value
Client	Requires Windows Vista, Windows XP, or Windows 2000 Professional.
Server	Requires Windows Server 2008, Windows Server 2003, or Windows 2000 Server.
Header	Declared in Esent.h.
Library	Use ESENT.lib.
DLL	Requires ESENT.dll.

JetTruncateLog Function