IVssBackupComponents::AddAlternativeLocationMapping method (vsbackup.h)

Article
10/13/2021

The AddAlternativeLocationMapping method is used by a requester to indicate that an alternate location mapping was used to restore all the members of a file set in a given component.

Syntax

HRESULT AddAlternativeLocationMapping(
  [in] VSS_ID             writerId,
  [in] VSS_COMPONENT_TYPE componentType,
  [in] LPCWSTR            wszLogicalPath,
  [in] LPCWSTR            wszComponentName,
  [in] LPCWSTR            wszPath,
  [in] LPCWSTR            wszFilespec,
  [in] bool               bRecursive,
  [in] LPCWSTR            wszDestination
);

Parameters

[in] writerId

Globally unique identifier (GUID) of the writer class that exported the component.

[in] componentType

Type of the component. The possible values of this parameter are defined by the VSS_COMPONENT_TYPE enumeration.

[in] wszLogicalPath

Null-terminated wide character string containing the logical path to the component.

For more information, see Logical Pathing of Components.

The logical path can be NULL.

There are no restrictions on the characters that can appear in a non-NULL logical path.

[in] wszComponentName

Null-terminated wide character string containing the component name.

There are no restrictions on the characters that can appear in a non-NULL logical path.

[in] wszPath

Null-terminated wide character string containing the path to the directory that originally contained the file to be relocated. This path can be local to the VSS machine, or it can be a file share directory on a remote file server.

The path can contain environment variables (for example, %SystemRoot%) but cannot contain wildcard characters. UNC paths are supported.

There is no requirement that the path end with a backslash (""). It is up to applications that retrieve this information to check.

[in] wszFilespec

Null-terminated wide character string containing the original file specification.

A file specification cannot contain directory specifications (for example, no backslashes) but can contain the ? and * wildcard characters.

[in] bRecursive

A Boolean value that indicates whether the path specified by the wszPath parameter identifies only a single directory or if it indicates a hierarchy of directories to be traversed recursively. This parameter should be set to true if the path is treated as a hierarchy of directories to be traversed recursively, or false if not.

For information on traversing mounted folders, see Working with Mounted Folders and Reparse Points.

[in] wszDestination

Null-terminated wide character string containing the name of the directory where the file will be relocated. This path can be local to the VSS machine, or it can be a file share directory on a remote file server. UNC paths are supported.

Return value

The following are the valid return codes for this method.

Value	Meaning
S_OK	Successfully added the alternate location mapping.
E_INVALIDARG	One of the parameter values is not valid.
E_OUTOFMEMORY	The caller is out of memory or other system resources.
VSS_E_BAD_STATE	The backup components object is not initialized, this method has been called during a restore operation, or this method has not been called within the correct sequence.
VSS_E_INVALID_XML_DOCUMENT	The XML document is not valid. Check the event log for details. For more information, see Event and Error Handling Under VSS.
VSS_E_OBJECT_NOT_FOUND	The specified component does not exist.
VSS_E_UNEXPECTED	Unexpected error. The error code is logged in the error log file. For more information, see Event and Error Handling Under VSS. Windows Server 2008, Windows Vista, Windows Server 2003 and Windows XP: This value is not supported until Windows Server 2008 R2 and Windows 7. E_UNEXPECTED is used instead.

Remarks

Windows 7, Windows Server 2008 R2, Windows Vista, Windows Server 2008, Windows XP and Windows Server 2003: Remote file shares are not supported until Windows 8 and Windows Server 2012.

The writerId, componentType, wszLogicalPath, and wszComponentName parameters identify a particular component, and the wszPath, wszFilespec, and bRecursive parameters identify the file set belonging to that component.

The combination of path, file specification, and recursion flag (wszPath, wszFilespec, and bRecursive, respectively) provided to AddAlternativeLocationMapping to be mapped must match that of one of the file sets added to a component using either IVssCreateWriterMetadata::AddFilesToFileGroup, IVssCreateWriterMetadata::AddDatabaseFiles, or IVssCreateWriterMetadata::AddDatabaseLogFiles.

Because AddAlternativeLocationMapping is used to notify a writer that an alternate location was used to restore all the files in a component, it should not be called for any component or files in a component that have not had an alternate location mapping specified.

The value of wszPath will have been mapped to wszDestination on restore; however, file names and subdirectories under the original path retain their same names.

A typical usage of AddAlternativeLocationMapping during restore might be the following:

Retrieve stored Writer Metadata Documents from the backup media and load that information with IVssExamineWriterMetadata::LoadFromXML.
Call IVssExamineWriterMetadata::GetAlternateLocationMapping to get an IVssWMFiledesc interface with the mapping information and use IVssWMFiledesc::GetAlternateLocation to get the alternate location.
Examine filedesc information to heuristically determine which component this alternate location mapping should be applied to.
Call IVssBackupComponents::AddAlternativeLocationMapping to communicate where files were restored.

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, if no valid alternate location mapping is defined this constitutes a writer error.

A file may 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.

Again, if no valid alternate location mapping is defined this constitutes a writer error.

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.

Requirements

Requirement	Value
Minimum supported client	Windows XP [desktop apps only]
Minimum supported server	Windows Server 2003 [desktop apps only]
Target Platform	Windows
Header	vsbackup.h (include VsBackup.h, Vss.h, VsWriter.h)
Library	VssApi.lib