ETI-NET

BackHome! backup-restore and BackHome! TMF option permit backup over an SNA network, to IBM tape units. This note addresses the product usage and evolution, with regard of tape management.

From the Tandem side

The Tandem programs (backup,restore or TMF) see a tape with unlimited capacity.

For backup/restore and TMF, there is no operation related to tape, there is even no "tape mount" issued by the operating system.

From the IBM side

To each Tandem tape, corresponds one IBM file, on disk or on tape. The largest files become multi-volume files on IBM.

Procedures identical to backup/restore procedures using the Tandem backup without Tape Catalog should be set up.

To know which backup object to use at restore time, a catalog of IBM file names (rather than Tandem tape volumes) should be kept. The IBM catalog and storage management facilities help. As example, Generation Data Groups allow automatic cleanup and easy addressing of a chosen version among last executions of a specific backup.

Tandem Tape Catalog is not supported yet. ETI is currently working on the support of various catalogs on Tandem. The catalog will register the backup objects and the disk files in each backup object. Also, a feature will be introduced to speed up the restore processing, when only a small part of the backup is to be restored.

Meanwhile, the traditional ways to help Tandem backup-restore can be used:

- keeping the backup control report

- execution of an LISTONLY restore

When the network is not available and when a compatible tape unit is accessible from the Tandem system, a provided utility allows to restore directly from the IBM tapes.

The user has first to inquire the IBM catalog to know the volumes on which the chosen backup is stored. The IBM filename and the list of volumes must be entered on Tandem to execute the stand-alone restore. The utility is expecting a mono or multi-volume IBM file on tapes with regular IBM labels.

Compatibility of Tandem and IBM tape units does not necessarily cover all features. Tandem unit may be unable to read tapes written on IBM if hardware compression feature is enabled.

Backup of an entire Tandem system over the network in an only one backup execution is avoided:

- a network failure will force the backup restart from the beginning

- the break down in several backup executions gives an other way to parallel execution, beside the BCOM multiplexing feature

- the restore of a partial backup will transmit less unused data over the network

BackHome!TMF maintains its own catalog to keep the correspondence between each tapemedia known by TMF and the current physical support for that tapemedia. The correspondence is automatically maintained by BackHome, except for stand-alone restore.

In BackHome catalog, each tapemedia may be:

- a regular Tandem local TMF tape, the tape volume is recorded

- a remote IBM file, the IBM file name is recorded

- a set of IBM tapes to read locally, the IBM file name and the list of volumes must be entered by the user

When recovering a file from the remote and/or local TMF tapes, there is no manual operation to identify the audit and online dump objects.

- TMF associates a dump to a tapemedia

- BackHome associates a tapemedia to an IBM file, or a local Tandem TMF tape

- MVS associates a file name to volumes

To recover a file when the dump objects are on IBM tapes and the network is not functional, a stand-alone recover from the IBM tapes is available.

The user will know the required tapemedia by a tape mount message on the Tandem console.

In the Tandem BackHome!TMF user interface, the catalog is inquired to know the IBM filename corresponding to the TMF tapemedia.

As for stand-alone-restore, the user has to inquire the IBM catalog to know the volumes on which the dump is stored.

The volumes must be entered in the Tandem BackHome!TMF user interface.

Finally a "reject tape mount" will force a retry, processed according to the new status of the BackHome catalog.