VSS_BACKUP_TYPE enumeration (vss.h)

  • Article

The VSS_BACKUP_TYPE enumeration indicates the type of backup to be performed using VSS writer/requester coordination.

Syntax

typedef enum _VSS_BACKUP_TYPE {
  VSS_BT_UNDEFINED = 0,
  VSS_BT_FULL,
  VSS_BT_INCREMENTAL,
  VSS_BT_DIFFERENTIAL,
  VSS_BT_LOG,
  VSS_BT_COPY,
  VSS_BT_OTHER
} VSS_BACKUP_TYPE, *PVSS_BACKUP_TYPE;

Constants

 
VSS_BT_UNDEFINED
Value: 0
The backup type is not known.


This value indicates an application error.
VSS_BT_FULL
Full backup: all files, regardless of whether they have been marked as backed up or not, are saved. This is
the default backup type and schema, and all writers support it.


Each file's backup history will be updated to reflect that it was backed up.
VSS_BT_INCREMENTAL
Incremental backup: files created or changed since the last full or incremental backup are saved. Files are
marked as having been backed up.


A requester can implement this sort of backup on a particular writer only if it supports the
VSS_BS_INCREMENTAL schema.

If a requester's backup type is VSS_BT_INCREMENTAL and a particular writer's
backup schema does not support that sort of backup, the requester will always perform a full
(VSS_BT_FULL) backup on that writer's data.
VSS_BT_DIFFERENTIAL
Differential backup: files created or changed since the last full backup are saved. Files are not marked as
having been backed up.


A requester can implement this sort of backup on a particular writer only if it supports the
VSS_BS_DIFFERENTIAL schema.

If a requester's backup type is VSS_BT_DIFFERENTIAL and a particular writer's
backup schema does not support that sort of backup, the requester will always perform a full
(VSS_BT_FULL) backup on that writer's data.
VSS_BT_LOG
The log file of a writer is to participate in backup or restore operations.


A requester can implement this sort of backup on a particular writer only if it supports the
VSS_BS_LOG schema.

If a requester's backup type is VSS_BT_LOG and a particular writer's backup
schema does not support that sort of backup, the requester will always perform a full
(VSS_BT_FULL) backup on that writer's data.
VSS_BT_COPY
Files on disk will be copied to a backup medium regardless of the state of each file's backup history, and
the backup history will not be updated.


A requester can implement this sort of backup on a particular writer only if it supports the
VSS_BS_COPY schema.

If a requester's backup type is VSS_BT_COPY and a particular writer's backup
schema does not support that sort of backup, the requester will always perform a full
(VSS_BT_FULL) backup on that writer's data.
VSS_BT_OTHER
Backup type that is not full, copy, log, incremental, or differential.

Remarks

An implementation of a backup type defined by a VSS_BACKUP_TYPE value must be done using the VSS API.

This is particularly true in the case of incremental (VSS_BT_INCREMENTAL) and differential (VSS_BT_DIFFERENTIAL) backups. In these cases, requesters and writers work together using the file backup specification masks (VSS_FILE_SPEC_BACKUP_TYPE), and designations of files as being part of partial and differenced file operations to select which files must be backed up.

A requester may also use other more traditional techniques to implement an incremental or differential restore, but it must not override the information provided through the VSS interfaces.

If a requester, when processing a given backup type, encounters a writer that does not support that backup type, the requester performs backup or restore operations for that particular writer's data as if the backup type was VSS_BT_FULL.

Requesters set the backup type with a call to IVssBackupComponents::SetBackupState.

Writers use CVssWriter::GetBackupType to determine the backup type.

Requirements

Requirement Value
Minimum supported client Windows XP [desktop apps only]
Minimum supported server Windows Server 2003 [desktop apps only]
Header vss.h

See also

CVssWriter::GetBackupType

IVssBackupComponents::SetBackupState