Repostor Backups

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Do you want to learn why
Database backups
are different from file backups?
Click HERE to find out.

Metro Mirror commands and Usage

So what sort of things would you want to do with Metro Mirror, and how would you do them? The following is a list of scenarios and the commands needed to make them happen.

Using the DS8700 CLI Interface

You can use the Command Line Interface on a DS8000 to configure Metro Mirroring for both Open Systems and mainframes. To run these commands you need to know the disk serial numbers, Subsystem IDs of logical controllers, and Path ports. Most of the commands below require -dev and -remotedev parameters. These are used to identify disk subsystems and the name is made up up maunufacturer.machine_type-serial_number. For the sake of illustration I'm using IBM.2107-75AK275 for the primary subsystem and IBM.2107-75MG701 for the secondary subsystem.
Mirroring is done by logical subsystem, so '5A' is the primary LSS and '5B' is the secondary LSS.
You will need to substitute your own values for these parameters.

Working with Paths

If you are establishing mirroring from scratch then the first thing you need to do is establish communications paths with the mkpprcpath command. When you run the mkpprcpath command, it does not add new paths onto existing paths. Rather the existing paths are deleted, then your paths are added. This means that if paths already exist and you are adding new ones, you must make sure the existing paths are included in your command. Use the lspprcpath command to check out existing paths.

lspprcpath -fullid 5A 5B

fullid means list out the fully qualified identifiers, and 5A and 5B are the logical subsystems.

The following command will define 4 paths, with details as follows
The source and remote subsystems are as defined above. You also need to define the WWNN of the remote subsystem, which is a 16 digit hex number. The one shown is a typical example. You could use the lssi or showsi command to find out your wwnn number.
the srclss and the tgtlss parameters refer to the logical subsystem IDs at source and remote, in this example, 5A and 5B
Last comes the Fiber Channel Port IDs, in source:target pairs. Each ID consists of I, the 2 digit port enclosure number, the adaptor number and the port number, which results in a number with format Innnn. Each source:target pair must be separated by a colon, with no spaces in between.

mkpprcpath -dev IBM.2107-75AK275 -remotedev IBM.2107-75MG701 -remotewwnn 50050A6307FEC268 -srclss 5A -tgtlss 5B I0103:I0103 I0233:I0233 I0503:I0503 I0633:I0633

If you want to know what Fiber Channel links are available, use

lsavailpprcport -dev IBM.2107-75AK275 -remotedev IBM.2107-75MG701 -remotewwnn 50050A6307FEC268 -l 5A:5B

To remove all the paths, use the rmpprcpath command

rmpprcpath -dev IBM.2107-75AK275 -remotedev IBM.2107-75MG701 -remotewwnn 50050A6307FEC268 5A:5A 5B:5B

List, Create or Delete Pairs

The following command with list out the mirroring status of disks 5A01-5AB3. The optional -l switch means display long output.

lspprc -dev IBM.2107-75AK275 -remotedev IBM.2107-75MG701 5A01-5AB3:5A01-5AB3

To set up pairs of metro mirroring disks, use the mkpprc command

mkpprc dev IBM.2107-75AK275 -remotedev IBM.2107-75MG701 -type mmir -mode full 5A01-5AB3:5A01-5AB3

The type parameter is set to mmir, which is metro mirror (synchronous). The mode full parameter means copy over all the data and make a full new copy at the remote site. The addresses at the end of the command are a source volume range which will be copied to a remote volume range. An equivalent global mirror command is

Suspend and Resume Mirroring

mkpprc dev IBM.2107-75AK275 -remotedev IBM.2107-75MG701 -type gcp -mode nocp -cascade 5A01-5AB3:5A01-5AB3

Here, type gcp is Global Copy (Asynchronous), mode nocp means just establish mirroring but don't do any initial data copying. The assumption is that both local and remote disks are identical. Cascade means that the target volumes are source disks for another Global Copy relationship.
To completely remove mirroring relationships between disks, use the rmpprc command

rmpprc dev IBM.2107-75AK275 -remotedev IBM.2107-75MG701 -type mmir -mode full 5A01-5AB3:5A01-5AB3 -quiet

You will normally be prompted with the usual 'are you really sure' messages if you run this command, the optional -quiet switch supresses these messages.

Freeze and Thaw

Freeze is used when there is a problem in the primary site. When freeze is issued, no IO is allowed to the primary disks (so applications hang), mirroring is suspended and the mirroring paths are deleted. The command to do this is freezepprc. The equivalent unfreezepprc command allows access to the primary disks again, but mirroring is still suspended. Example commands are:

  freezepprc dev IBM.2107-75AK275 -remotedev IBM.2107-75MG701 5A:5B unfreezepprc dev IBM.2107-75AK275 -remotedev IBM.2107-75MG701 5A:5B

Pause and Resume mirroring

It is possible to temporarily suspend mirroring for a while without affecting live applications. Updates to primary disks are logged and are copied over to the target disks when mirroring is resumed again. The commands to do this are

 pausepprc dev IBM.2107-75AK275 -remotedev IBM.2107-75MG701 5A01-5AB3:5A01-5AB3 resumepprc dev IBM.2107-75AK275 -remotedev IBM.2107-75MG701 5A01-5AB3:5A01-5AB3

Failover and Failback

Failover means change mirroring so the target volumes become the primaries and the source volumes become the secondaries. The mirroring direction is reversed. Failback is the reverse, except that any changed data on the old target volumes is copied over to the old source volumes, then mirroring is resumed back in the normal direction again. The type is shown as mmir, but it could be gcp.

failoverpprc dev IBM.2107-75AK275 -remotedev IBM.2107-75MG701 -type=mmir 5A:5B failbackpprc dev IBM.2107-75AK275 -remotedev IBM.2107-75MG701 -type=mmir 5A:5B

Using Mainframe TSO commands

This section is about the Mainframe TSO commands that can be used to manage Metro Mirror between two storage subsystems. There are several good IBM manuals which describe the commands used to drive Metro Mirror. Rather than just repeat that information, the table concentrates on what the commands are used for. You can run the commands from TSO, or as an ICKDSF batch job. The equivalent CLI command is also shown.

TSO Command ICKDSF Command DS CLI Command Action
CESTPATH / CDELPATH PPRCOPY ESTPATH / DELPATH mkpprc / mkpprcpath to define or delete paths between storage subsystems
CESTPAIR / CDELPAIR PPRCOPY ESTPAIR / DELPAIR rmpprc / rmpprcpath to define or remove mirrored volumes
CGROUP FREEZE PPRCOPY FREEZE freezeprc to freeze mirroring on a group of disks
CGROUP RUN PPRCOPY RUN unfreezepprc to re-establish mirroring on a group of disks
CQUERY PPRCOPY QUERY lspprc to find out the PPRC mirroring status of a disk.
CRECOVER PPRCOPY RECOVER rmpprc -at src to make a mirrored secondary volume available for use
CSUSPEND PPRCOPY SUSPEND pausepprc to temporarily suspend mirroring
CESTPAIR ACTION(FAILOVER) PPRCOPY ESTPAIR FAILOVER failoverpprc temporarily failover to secondary site, record changes on secondary volumes
CESTPAIR ACTION(FAILBACK) PPRCOPY ESTPAIR FAILBACK failbackpprc failback to primary site, copy changed data over to primary volumes

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