Data Movement Between Different DASD

The FDR system can be used to move or restore data from one DASD device type to another. This section describes some of the techniques and rules for doing so.

A DASD device is characterized by the maximum number of bytes that can be written on a track, and by the number of tracks in a cylinder; these are called its “device geometry”. FDR considers two DASD to be “unlike” devices if either of those two values is different. For example, a 3380 and a 3390 DASD have the same tracks/cylinder (15) but the bytes/track is different (47476 vs. 56664) so FDR treats them as unlike devices.

However, within a type of DASD, such as 3380 or 3390, there are different models that have a different total number of cylinders. Some DASD subsystems allow you to define DASD of any arbitrary size. Despite the difference in size, these are considered “like” devices for restore. The number of cylinders is sometimes called the “density”; two DASD with different density have the same geometry but different cylinder count.

Full-volume restore

An FDR or ABR full-volume restore (RESTORE TYPE=FDR) can be used only to restore to like devices, DASD of the same geometry which may differ in size (total number of cylinders). Since full-volume restore rewrites the exact images of the original tracks, it cannot restore to an “unlike” device since the data would not be formatted properly for the different device geometry.

Restores to a volume with a larger number of cylinders than the original DASD are fully supported by FDR and ABR. Since all of the tracks being restored exist on the output DASD, they can all be restored properly. All that is required is to make the excess tracks available as free space for allocation of new data sets.

Restores to a volume with a smaller number of cylinders can also be done, as long as the original volume has no data sets allocated on cylinders that do not exist on the output DASD. To enable this restore, specify the PROT=NONE operand on the RESTORE or COPY TYPE=FDR statement. Tracks that no longer exist are removed from the free space on the volume. However, COMPAKTOR is a preferable method for doing this conversion, as described later in this chapter.

To update the free space, at the end of the restore, FDR sets the DOS flag in the Format 4 DSCB in the VTOC, telling z/OS that the free space DSCBs are invalid and must be rebuilt. Then a dummy data set is allocated causing this to occur. The dummy data set's name is:

FDRABR.VvolserZ

where “volser” is the DASD volume serial number. However, this allocation is designed to fail and causes an IEC614I message in the job log; this is expected and is sufficient to cause the free space DSCBs to be rebuilt to reflect the new size of the volume. Your security system, if any, must allow the allocation of this data set for the free space update to occur. This allocation does not work on SMS-managed volumes; you receive message FDR341 with COMP=192 and must manually allocate a data set on the volume to update the free space.

If the original volume had an active indexed VTOC, it is disabled after the restore and must be rebuilt by the user (see Rebuild Indexed VTOC Example in Section FDR-RESTORE-Examples). This is especially important on SMS-managed volumes.

After a full-volume restore, all data sets, including the VTOC, indexed VTOC, and VVDS, have the same size and position as they had on the original DASD. If they were small on the original DASD, they may not be large enough to handle new data sets allocated on the larger DASD, so you may need to increase their size. The IBM ICKDSF manual has guidelines for sizing the VTOC and VTOCIX.

Full-volume copy

An FDR full-volume disk-to-disk copy (COPY TYPE=FDR) can also copy between different densities of the same DASD type. The rules are the same as for a full-volume restore.

COMPAKTOR

A COMPAKTion from a backup (not a “Fast COMPAKTion”) is essentially a full-volume, track-image restore, so COMPAKTOR is also limited to restoring to like DASD with the same geometry.

A COMPAKTOR restore to a different density DASD has several advantages over an FDR full-volume restore:

  • Since COMPAKTOR can move data sets during the restore, it automatically moves data sets to fit in the new space.
  • When restoring to a smaller DASD, it relocates all data sets to fit unless the total tracks required exceeds the capacity of the output DASD, or there are unmovable data sets that are located beyond the end of the new DASD.
  • If there is insufficient space, the SELECT statement operand SCRATCH=YES is used to eliminate selected non-VSAM data sets until the remaining data sets do fit (for non-SMS volumes only).
  • COMPAKTOR can move the VTOC to an appropriate location on the output DASD. It can also expand the VTOC, which may be required on a larger DASD since more data sets may be allocated there.
  • COMPAKTOR can move (but not expand) the indexed VTOC and VVDS.
  • COMPAKTOR automatically rebuilds the Format 5 or Format 7 DSCBs indicating the proper free space for the size of the output DASD.
  • If the volume had an active indexed VTOC, COMPAKTOR automatically rebuilds the indexed VTOC.

Since a Fast COMPAKTion (FASTCPK) always reorganizes one online DASD, unlike device is not an issue.

Data set restore

A DSF or ABR data set restore can be done to a “like” device or, in most cases, to an “unlike” DASD device.

When restoring to a “like” DASD device, all densities and models of the DASD are treated the same, since the DASD geometry is the same. A “physical” track-image restore is done (unless BLKF= is specified to re-block PS data sets). If the output data set must be allocated, there must be sufficient free space on the volume to contain the data set. For example, a data set that occupied an entire 3390-3 cannot be restored to a smaller 3390 and a 100-cylinder data set must be restored to a volume with at least 100 free cylinders (in 5 or fewer extents), unless the space requirement is overridden by the user. Details on how physical device restore handles various data set types are in FDR-Processing-by-Type-of-Data-Set.

Data set restore has no facility for “breaking apart” a single data set onto multiple volumes. Likewise, a data set that was in multiple parts on several original DASD volumes cannot be combined into one piece on a larger DASD; it must be restored to as many DASD volumes as it was dumped from. Data sets that were marked as “unmovable” and were allocated in the higher tracks of a larger DASD cannot be allocated on a smaller DASD, since those tracks are not available.

A “logical” restore is done when restoring a data set to an “unlike” DASD since their device geometry differs. Although the original backup is still in track-image format (FDR has no need to do a special logical backup), the data is extracted and reformatted for the new device type. The amount of space required for each data set is adjusted so that the output data set occupies about as many bytes as the data set did on its original DASD. Details on logical restore of various data set types are also in FDR-Processing-by-Type-of-Data-Set.

A logical restore may also be done if data set reblocking is requested, or for data set types requiring special processing.

When restoring to a new DASD volume serial, DSF and ABR can recatalog the data set to the new DASD, if the RECAT (for non-VSAM data sets) and VRECAT (for VSAM clusters) operands are specified. VRECAT deletes the original cluster if it still exists.

Data set copy and move

FDRCOPY can copy or move data sets to “like” and “unlike” devices, under the same rules as for data set restore (FDRCOPY is essentially a track-image dump and a physical or logical restore in the same step). Although FDRCOPY is a fast way of moving data sets to a new DASD, and can run without operator intervention (tape mounts), no backup is created by FDRCOPY.

Converting to larger DASD

Often, an installation replaces DASD of one capacity with “like” DASD of a larger capacity (such as replacing 3390-3 DASD with 3390-9 DASD). The lower density DASD may need be combined onto a smaller number of high-density DASD.

If possible, one of the original DASD can be directly converted to a larger DASD under its original volume serial. This can be done with an FDR or ABR full-volume restore, an FDR full-volume COPY, or COMPAKTOR. Since data sets restored by a full-volume operation are NOT recataloged, this restore MUST be done using the original volume serial (CPYVOLID=YES). COMPAKTOR is preferable for this operation since it can expand and relocate the VTOC. Examples of full-volume conversion can be found in FDR-RESTORE-Examples, FDR-DASD-COPY-Examples, and COMPAKTOR-Examples”. Data sets from other original volumes can be added to the larger DASD with DSF, FDRCOPY, or FDRMOVE as described below.

If the full-volume operation is not possible (if, for example, the new DASD must have new volume serials), then ALL of the original data sets must be moved with DSF, FDRCOPY, or FDRMOVE.

To move data sets to the larger DASD:

  • FDRCOPY can easily move all data sets on a volume to a new volume. This is the recommended method. An FDRCOPY MOVE automatically re-catalogs data sets to the new volume. Examples can be found in FDRCOPY-Data-Set-MOVE-Examples. See Multi-Volume VSAM Considerations in VSAM-Special-Considerations for considerations on moving multi-volume VSAM clusters.
  • DSF can restore all data sets from an FDR full-volume backup or DSF backup of the original DASD volumes. RECAT and VRECAT should be specified so that all data sets are cataloged on the new volume. DSF-Non-SMS-Managed-RESTORE-Examples contains an example.
  • FDRMOVE (a separately priced product from BMC Corporation) provides a high-performance, non-disruptive or minimally-disruptive movement of z/OS data sets. It is ideal for volume consolidation (for example, consolidating data from three 3390’s to a single 3390-9).

Converting to smaller DASD

It may be necessary to fall-back or convert from high-density DASD to lower-density DASD of the same type (such as from 3390-9 DASD to 3390-3 DASD or 3390-27 to 3390-9).

If all the data sets on the larger DASD fit on the smaller DASD, then a full-volume restore or COMPAKTion may be used to do the conversion, as described earlier in this section.

In most cases, the data does not fit on a single output DASD, and must be spread over multiple output DASD volumes. The DSF, FDRCOPY, and FDRMOVE techniques just described for converting to hi-density DASD can also be used for conversion to lower-density DASD. The NVOL= operand on SELECT statements for DSF, ABR, FDRCOPY, or FDRMOVE must specify multiple DASD volumes, for example, NVOL=(PROD01,PROD02,PROD03) or NVOL=PROD* that spread the selected data sets over the indicated volumes. Examples for DSF and FDRCOPY are found in DSF-Non-SMS-Managed-RESTORE-Examples and FDRCOPY-Data-Set-MOVE-Examples. Examples for FDRMOVE are found in the FDRPAS space.

Converting to new DASD types

Since full-volume operations do not work with “unlike” DASD devices, only data set operations can be used to convert data sets to a new DASD device type (such as 3380 to 3390). The DSF, FDRCOPY, and FDRMOVE techniques just described for conversion between models of “like” DASD can be used for “unlike” conversion.

However, there are special considerations and restrictions on certain data set types; the details are in FDR-Processing-by-Type-of-Data-Set.

FDRPAS

FDRPAS, a separately priced product from BMC Corporation, can be used to non-disruptively move volumes from one device to another, while they are in use. FDRPAS only moves to like device types, such as 3390 to 3390, but it can move to larger DASD and, in some circumstances, to smaller DASD. FDRPAS is often used to move volumes to new DASD hardware without interrupting normal use of the volumes. Contact BMC for more information on FDRPAS.

 

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