IVssComponent::GetAlternateLocationMapping method

The GetAlternateLocationMapping is used to return a file set's alternate location for file restoration. This method can be called by either a writer or a requester.


HRESULT GetAlternateLocationMapping(
  [in]        UINT           iMapping,
  [out] const IVssWMFiledesc **ppMapping


iMapping [in]

Index of a particular mapping. The value of this parameter is an integer from 0 to n–1 inclusive, where n is the total number of alternate location mappings associated with the current component. The value of n is returned by IVssComponent::GetAlternateLocationMappingCount.

ppMapping [out]

Doubly indirect pointer to a IVssWMFiledesc object containing the mapping information.

Return value

The following are the valid return codes for this method.


Successfully returned the attribute value.


One of the parameter values is not valid.


The caller is out of memory or other system resources.


The XML document is not valid. Check the event log for details. For more information, see Event and Error Handling Under VSS.


The specified item was not found.



Alternate location mappings returned by GetAlternateLocationMapping can come not only from files in the current component, but also from files in any of its nonselectable subcomponents.

The value returned by IVssComponent::GetAlternateLocationMapping should also not be confused with that returned by IVssExamineWriterMetadata::GetAlternateLocationMapping:

A file should always be restored to its alternate location mapping if either of the following is true:

  • The restore method (set at backup time) is VSS_RME_RESTORE_TO_ALTERNATE_LOCATION.
  • Its restore target was set (at restore time) to VSS_RT_ALTERNATE.

In either case, having no alternate location mapping defined constitutes a writer error.

A file can be restored to an alternate location mapping if either of the following is true:

  • The restore method is VSS_RME_RESTORE_IF_NOT_THERE and a version of the file is already present on disk.
  • The restore method is VSS_RME_RESTORE_IF_CAN_REPLACE and a version of the file is present on disk and cannot be replaced.

An alternate location mapping is used only during a restore operation and should not be confused with an alternate path, which is used only during a backup operation.

The mapping returned by GetAlternateLocationMapping refers to the alternate location mappings used in the course of restoring files.

Alternate location mappings are added to an IVssComponent object by IVssBackupComponents::AddAlternativeLocationMapping.

The caller must call IUnknown::Release to release the system resources held by the ppMapping parameter when it is done with the IVssWMFiledesc object that it points to.

For more information on backup and restore file locations under VSS, see Non-Default Backup And Restore Locations.


Minimum supported client

Windows XP [desktop apps only]

Minimum supported server

Windows Server 2003 [desktop apps only]


VsWriter.h (include Vss.h or VsWriter.h)



See also