How to setup Snapshot General Services for Database Management for Db2 tools

Products

• Quick Copy for DB2 for z/OS

Issue/Introduction

How to setup Snapshot General Services to exploit Flash Copy hardware features using Quick Copy for Db2 for z/OS.

Resolution

There are essentially three components to using Snapshot General Services.

1. CAIRIM         -  Initialize Snapshot General Services during IPL
2. Quick Copy   -  Snapshot keywords are used to request a Snapshot copy
3. Xmanager     -  Monitors Quick Copy copies only when Quick Copy keyword SNAPSHOTACCESS INSTANT is specified

Snapshot support is mostly transparent. The initialization parameters specified when Snapshot General Services is initialized by CAIRIM define the mappings between source data sets and their copies (names and volumes). When Snapshot is then requested through a utility, such as Quick Copy for Db2 for z/OS, the rest is automatic.

1. CAIRIM
   
   You will more than likely already have CAIRIM (Resource Initialization Manager) installed at your site as this is the command driver which as part of Common Services, prepares and starts all your applications. It is also used to manage the Broadcom license keys.
   
   The installation of Broadcom products requires LMP license keys and the installation of the CA Common Services for z/OS CAIRIM Service for product licensing authorization.
   Common Services is delivered and installed separately. Please refer to the Common Services for z/OS documentation for more information.
   
   The Snapshot General Services subsystem is typically initialized by CAIRIM at IPL time. To do this you must add a command to the CAIRIM startup parameters. The startup parameters are in the data set or member allocated to the PARMLIB DD statement in the CAIRIM started task procedure.
   
   To initialize Snapshot General Services add the following command to the CAIRIM started task procedure:
   
   PRODUCT(desc) VERSION(vers) INIT(name) PARM(parm)
   
   desc - Solution or service description (up to 20 characters). This parameter is specified once for each product to be installed. In this case the PRODUCT description of 'Snapshot Gen Service' can be used.
   
   PRODUCT(Snapshot Gen Service) VERSION(TG10) INIT(TG10INIT) - PARM(parameters)
   
   The parameter statements in the Snapshot General Services parameter file are used to map source volumes to target volumes and specify global options.
   
   A sample parameter library definition is provided in highlvl.PARMLIB(TGRPARM).
   
   
2. Quick Copy
   
   To request Snapshot point-in-time copies through Quick Copy specify the following Quick Copy keywords:
   
   SNAPSHOTACCESS specifies whether to take a SNAPSHOT point-in-time copy for the selected objects.
   SNAPSHOTFALLBACK specifies the action to take if an error occurs during a SNAPSHOT point-in-time copy.
   SNAPSHOTHLQ defines the high level qualifier to use for the Snapshot point-in-time copies.
   
   
3. Xmanager
   
   Xmanager monitors Quick Copy copies when SNAPSHOTACCESS INSTANT is specified. SNAPSHOTACCESS INSTANT is used to create copies that can be used by Fast Recover for DB2 for
   z/OS for instant restores. Xmanager tracks the physical copy process and has commands that allow the status of copies to be displayed or changed. However, Xmanager does not get involved
   with SNAPSHOTACCESS YES copies, so if you are not using SNAPSHOTACCESS INSTANT, your copies will not be affected by messages located within Xmanager.
   
   When Xmanager starts up it attempts to connect to a Snapshot subsystem. By default it connects to CATG the master Snapshot subsystem. (This is the default if you do not specify the
   SUBSYS() keyword on the Snapshot initialization job. If you want it to connect to a different Snapshot subsystem, you can put a //TGRSUBSY DD SUBSYS=xxxx DD statement in the Xmanager
   procedure. "xxxx" is the same subsystem name specified on the SUBSYS() keyword on the Snapshot initialization job. If Xmanager cannot find the Snapshot subsystem a TGR004 message is
   issued and the Xmanager/Snapshot interface is shut down.
   
   When Xmanager connects to a Snapshot subsystem, its XMANID is stored in a field in a Snapshot control block. When Xmanager starts, it checks this field, if it is null, it puts its own XMANID in
   it. If the field is not null, Xmanager checks to see if it matches it's own XMANID. If it does not, it issues a TGR007 message, and the Xmanager/Snapshot interface is shut down.
   
   The purpose of this check is to make sure that we do not have two Xmanager started tasks connected to the same Snapshot subsystem. That would cause confusion about which Xmanager was
   monitoring and controlling SNAPSHOTACCESS INSTANT copies. So if you start two Xmanager tasks, both of which point to the same Snapshot subsystem, only one of them will connect it's
   Xmanager/Snapshot interface with the Snapshot subsystem. This one will monitor SNAPSHOTACCESS INSTANT copies. The other Xmanager task will issue a TGR007 message and shut
   down it's Xmanager/Snapshot interface.
   
   If you start an Xmanager task that connects to a Snapshot subsystem, then you stop and re-start the Xmanager task with a different XMANID, the Xmanager task will issue a TGR007 message
   and shut down its Xmanager/Snapshot interface. If you re-initialize the Snapshot subsystem, and then re-start the Xmanager task, it will connect properly.