Overview of FDRINSTANT for Hitachi ShadowImage

FDRINSTANT and Hitachi ShadowImage

FDRINSTANT™ is an additional cost FDR facility for non-disruptive backup. It works in concert with ShadowImage®, a licensed feature of Hitachi Vantara DASD subsystems that allow for the “instant” creation of exact duplicates of existing DASD volumes.

FDRINSTANT enhances:

  • FDR full volume backup
  • FDRDSF data set backup
  • FDRCOPY data set copy
  • FDRABR volume backup (full-volume and incremental backup).

It provides non-disruptive backup of offline operating system DASD volumes, both SMS-managed and non-SMS volumes, using technology developed by BMC.

Traditional backups may disrupt normal operations. It obviously takes time to backup a data set or volume. If data sets are being updated by some application while they are being backed up, the backup may not be valid and the data sets may not be usable when they are restored. The usual response to this problem is to quiesce all updates to the data during the backup, disrupting normal operation until the backup is complete.

When used with Hitachi’s ShadowImage feature, FDRINSTANT allows you to instantly freeze a copy of an online DASD volume and easily backup or copy data from that point-in-time copy as if it was coming from the original volume. Updates to the data need to be quiesced only for the few moments necessary to create the point-in-time copy, if at all.

FDRINSTANT supports some additional features of ShadowImage. These features are supported directly when FDRINSTANT is used with FDRABR but they can also be used with FDR, FDRDSF, and FDRCOPY if you invoke them yourself:

ShadowImage Quick Split

Allows ShadowImage to operate more like IBM FlashCopy, where the ShadowImage pairs do not need to be predefined. For more information, see Quick-Split-Support.

ShadowImage Consistent Split

(Splitting multiple ShadowImage volumes at the same point-in-time). For more information, see FDRINSTANT-for-SnapShot-Consistent-Backup-Support.

TrueCopy

FDRINSTANT supports TrueCopy that can be used within a DASD subsystem or between two subsystems. TrueCopy does not support Quick Split.

FlashCopy

Hitachi DASD subsystems have an extra cost option that emulates IBM FlashCopy, so the FlashCopy support in FDRINSTANT works on a Hitachi Vantara system with their FlashCopy option installed. FlashCopy may be simpler to implement than ShadowImage. There are no extra FDR licensing requirements for use of FlashCopy on Hitachi; if you are licensed for FDRINSTANT for ShadowImage, then the FDRINSTANT FlashCopy support works automatically if FlashCopy is installed on the Hitachi subsystem. For documentation on FlashCopy usage with FDRINSTANT, see FDRINSTANT-for-FlashCopy.

FDRINSTANT enhances FDR components

FDRINSTANT enhances FDR, FDRDSF, FDRCOPY, and FDRABR (Volume Backups) to read from an offline copy of an online volume that was created as a point-in-time image using ShadowImage. This creates a backup or copy of the volumes or data sets that looks exactly like a normal backup or copy, except that the data is frozen in time.

If you are licensed for FDRABR, FDRINSTANT enhances ABR Volume Backups, both full-volume (TYPE=FDR) and incremental (TYPE=ABR/DSF/AUTO) to use ShadowImage, by creating “instant” point-in-time copies of the volumes to be backed up, and then moving that captured data to tape.

Hitachi Vantara volume imaging options

The Hitachi storage subsystems have several optional features that can be used with FDRINSTANT:

  • Hitachi TrueCopy is a remote mirroring feature from Hitachi Vantara storage arrays available for both open systems and IBM z/OS. TrueCopy is an implementation of IBM’s PPRC protocol that mirrors volumes between or within control units using a direct cable connection.
  • “Internal Remote Copy” allows creation of a second copy of a volume in the same subsystem with its own operating system address using TrueCopy. It requires an external PPRC cable.
  • The ShadowImage feature allows multiple clone images of an original volume in the same subsystem. No external cable is required.

The rest of this document refers only to ShadowImage, but all three features can be used with FDRINSTANT. Quick Split is only supported with ShadowImage.

These features automatically mirror any updates to the online volume to all of its copies, keeping all of them in synchronization with the online volume. The ShadowImage volumes:

  • Have their own device addresses.
  • Are not permanently assigned (paired) to any online volume.
  • Can be established to online volumes as a copy of any online volume in the DASD subsystem with the same device format and size. When initially established, all data on the online volume is internally copied to the paired secondary volumes. After this copy completes, all updates to the online volume are mirrored to the paired secondary volumes.
  • Can be detached from its current online volume by totally breaking the connection (resetting to simplex mode). At this point the secondary volume is a point-in-time image of the online volume and can be read or written, but no connection to the online volume is maintained; if it is again established to the online volume, the entire contents of the online volume must be recopied to the secondary.
  • Can be split from its current online volume by suspending the copy. At this point the secondary volume is a point-in-time image of the online volume and it can be read (Internal Remote Copy) or read and written (ShadowImage). While suspended, the control unit records what tracks on the online volume and the split secondary volume have been updated; when the pair is resynchronized, only those updated tracks are copied to the secondary, bringing the volumes back into synchronization much more quickly.

Under z/OS, you use the standard IBM PPRC (Peer to Peer Remote Copy) commands to manage ShadowImage volumes, including:

  • The TSO commands CQUERY, CESTPAIR, CSUSPEND, and CDELPAIR.
  • The ICKDSF PPRCOPY sub-commands QUERY, ESTPAIR, SUSPEND, and DELPAIR.

The TSO and ICKDSF commands have identical functions but different syntax. Consult the appropriate IBM manuals for details. Examples of the syntax of each are shown in this chapter.

Your Hitachi Vantara Account team can provide you with more information on ShadowImage.

ShadowImage without FDRINSTANT

Although ShadowImage can quickly create a point-in-time image of a production DASD volume, traditional backup products can not directly use the ShadowImage volume image without additional considerations.

For example, a conventional backup product requires that the detached ShadowImage volume be brought online. Since the operating system does not let you put two volumes with the same volume serial online, the ShadowImage volume serial must be changed.

Standard operating system utilities (for example, ICKDSF) provide a facility for re-labeling a ShadowImage volume after it is detached, but re-labeling a volume invokes additional requirements for SMS-managed volumes, VSAM clusters and cataloged data sets. The data sets on the re-labeled volume will appear to be uncataloged, which may cause problems during backup and restore unless they are renamed and recataloged.

A backup of a re-labeled volume appears to be a backup from the new volume serial, not the original volume serial, so additional procedures are required to document this correspondence (for example, backup of volume “B” is really a backup of volume “A”). Restore procedures must be modified to restore the backups to the correct volume serial (for example, restore volume “B” back to volume “A” and re-label it as “A”).

Hitachi provides a software utility to rename and re-catalog the data sets on the ShadowImage volume after the split. Although this could be used to backup those data sets with a standard backup utility, the installation must now use special procedures to restore each data set from its temporary name on the backup to its true name on the online volume. For large numbers of data sets, this could be onerous.

The FDRINSTANT solution

FDRINSTANT allows you to create and use a duplicate ShadowImage volume image without changing its volume serial or bringing it online. FDR full volume backup, FDRDSF data set backup and FDRCOPY data set copy use FDRINSTANT technology to read the detached ShadowImage volume even while it remains offline. A non-disruptive backup or copy can start as soon as the ShadowImage volume is detached. Updates to the online volumes continue while you create the point-in-time backup or copy of the data.

For FDRABR, FDRINSTANT makes volume backups a two-step process. The first step executes a PSPLIT statement under FDRABR, to split previously established ShadowImage copies of the selected volumes. If the copy is fully synchronized with its online volume, this takes only seconds per volume. The split copy is actually a valid backup at that point-in-time; you can do a restore from it if full-volume or data set recovery is required. The second step executes a normal FDRABR full-volume or incremental backup of the same volumes, except that ABR will read the offline point-in-time image and move it to a backup on tape. There is no need to identify the ShadowImage device to ABR; it knows the ShadowImage volume address of any given online volume.

You invoke FDRINSTANT for FDR, FDRDSF, and FDRCOPY with standard FDR JCL that points to the online volume but which contains a special data set name that identifies the offline ShadowImage volume just split from the online volume. FDRINSTANT verifies that the ShadowImage device is offline and that its volume serial matches the serial of the online DASD. It then reads the offline DASD in exactly the same way that it would read the online DASD. FDRINSTANT produces a backup that appears to be a conventional backup of the online volume serial. FDRINSTANT blends its unique off-line, high-speed non-disruptive backup together with a traditional restore complete with FDR’s powerful logical file capability.

There are no special considerations for restores from a backup created by FDRINSTANT. You can restore entire volumes or individual data sets from those backups. The target volumes for restore are online volumes, not the ShadowImage volumes. Since the backups created by FDRINSTANT appear to be backups of the online volume, there is no special volume serial or data set name concerns.

When FDRINSTANT is used with FDRCOPY, you can freeze a ShadowImage volume image of the online volumes containing the desired data sets, and then create copies of those data sets on other online volumes. Data sets can be renamed and cataloged during the copy.

 

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