Backing up critical Rational ClearCase data

Like all databases, VOBs, views, and the Rational® ClearCase® registry have special backup and restore requirements.

Ensuring frequent, reliable backups of essential data is a critical task for any Rational ClearCase administrator. Data in multiple repositories is often related, especially if you use UCM, so your backup routine must recognize and preserve those relationships. These topics describe backup procedures for VOBs, views, and the Rational ClearCase registry. Restore procedures are described in Restoring critical Rational ClearCase data.

Requirements for VOB and view backup tools

VOB and view data is stored in ordinary files and directories. It can be backed up with any tool that is appropriate for file-system backups as long as the tool captures all the necessary data and you follow the procedures in this chapter. When selecting a VOB or view backup tool, consider these requirements and recommendations:

The backup tool must be able to back up the largest file in the VOB. On many platforms, native backup utilities such as tar and cpio have limited abilities to back up large files or to create large archives. VOBs that are at schema version 54 can include string files that are larger than 2 GB. VOBs that are at feature level 5 can include container files that are larger than 2GB. Verify that the backup utility you use can accommodate the largest files the VOB can hold, and can create an archive large enough to back up the entire VOB. Backups that do not capture all the VOB files, regardless of how many or how large they are, do not restore correctly.
The backup tool must preserve NTFS ACLs. On Windows® platforms where VOB or view storage is located on an NTFS file system, the NTFS ACLs on the VOB or view storage directory are important. Unless your VOB and view storage is on a FAT file system (not recommended), any Windows backup tool you use must be able to back up and restore NTFS ACLs.
The backup tool should back up files even if they are open for writing. On all supported operating systems, VOB server processes keep VOB database files open for writing even when the VOB has been locked for backup. Unless you lock the VOB and stop Rational ClearCase on the VOB host during VOB backup, the program you use to back up VOBs must be able to back up files that are open for writing. Many common Windows backup tools and file-system copy utilities such as copy and xcopy do not have this capability and skip files that are open for writing, which renders the backup useless.
The backup tool should preserve file access times. On some platforms running Linux® or the UNIX® system, the tar utility, which is often used for backups, resets file access times. This can disrupt DO and cleartext storage pool scrubbing patterns (see Scrubbing VOB storage pools) and might prevent these pools from ever being scrubbed. The cpio utility, which is supported on hosts running Linux or the UNIX system, might be a better choice for VOB backup.

Note: Any backup procedure in this chapter can be used for a VOB or view that has its database on a supported network-attached storage (NAS) device. If you locate a VOB storage directory on such a device, you might be able to take advantage of device-specific backup utilities that can dramatically reduce VOB lock time. For information about supported NAS devices and their backup utilities, see the IBM Rational ClearCase Platforms Guide.

VOB backup strategies
An effective VOB backup strategy must provide maximum coverage while minimizing disruptions to ongoing VOB access.
Backing up VOBs with vob_snapshot
The vob_snapshot utility automates snapshot backups.
Backing up VOBs with standard backup procedures
If you do not use the vob_snapshot utility, you must take special precautions to ensure the integrity of VOB backups made with standard backup tools.
Backing up a view
The contents of views, unlike that of VOBs, can usually be reconstructed easily. With the exception of changes to checked-out versions and other view-private files, the contents of any view can be recovered by re-creating the view. Regular backups of views can still be important, especially if users are not in the habit of checking in their work regularly.
Backing up Rational ClearCase registry data
Rational ClearCase registry data is stored in ordinary files that must be backed up regularly.
Backing up related databases together
Data in multiple repositories is often related, especially when UCM is in use. Related databases should be backed up together.

Parent topic: Administering Rational ClearCase