Considerations

This section covers considerations that relate to DFSMShsm fast replication setup and administration.

3.5.1 DB2

If you want to set up a DFSMShsm fast replication environment for DB2, and you plan to take full system backups, a copy pool that consists of the active logs and bootstrap data sets (BSDS) is required.

The copy pool naming convention for DB2 is DSN$locn-name$cp-type:

򐂰 DSN is the unique DB2 product identifier.

򐂰 $ is a required delimiter.

򐂰 locn-name is the DB2 location name.

򐂰 cp-type is the copy pool type; use DB for database or LG for logs.

For example, DB2 DB1P has copy pools that are named DSN$DB1P$DB and DSN$DB1P$LG.

POOL STORAGE GROUP ALTER Page 1 of 2 Command ===> SCDS Name . . . : SYS1.SMS.SCDS Storage Group Name : SG1 To ALTER Storage Group, Specify: Description ==> ==> Auto Migrate . . N (Y, N, I or P) Migrate Sys/Sys Group Name . . Auto Backup . . N (Y or N) Backup Sys/Sys Group Name . . Auto Dump . . . N (Y or N) Dump Sys/Sys Group Name . . . Overflow . . . . N (Y or N) Extend SG Name . . . Copy Pool Backup SG Name . . . CPBSG1 Dump Class . . . (1 to 8 characters) Dump Class . . . Dump Class . . . Dump Class . . . Dump Class . . . ALTER SMS Storage Group Status . . . N (Y or N) Use ENTER to Perform Selection; Use DOWN Command to View next Page; Use HELP Command for Help; Use END Command to Save and Exit; CANCEL to Exit.

For more information, see Chapter 8, “Using DFSMShsm fast replication” on page 165, which is about using DFSMShsm fast replication in a DB2 environment, or DB2 UDB for z/OS V8: Through the Looking Glass and What SAP Found There, SG24-7088.

3.5.2 SMS constructs that span storage controllers

Volumes of the following constructs can span volume controllers (Figure 3-10 on page 41):

򐂰 Copy pools

򐂰 Storage groups

򐂰 CPBSGs

Especially if a storage group spans volume controllers, the associated CPBSG must span storage controllers, as well. FlashCopy targets must always be in the same storage controller as their source volumes. Therefore, you need to ensure that the one associated CPBSG contains enough volumes from all storage controllers according to copy pool settings and the number of source volumes in each storage controller.

Example 3-1 describes the constructs CP01, SG3, and CPBSG3 that are used in Figure 3-10 on page 41.

Example 3-1 SMS construct descriptions

Copy pool CP01: 4 backup versions with background copies of SG3

SG3: 3 volumes in the first storage controller, 2 volumes in the other one

CPBSG3: 3*4=12 volumes in the first storage controller, 2*4=8 volumes in the other one

If occasionally volumes of another storage controller will be added to SG1, the new scenario looks similar to what we see with CP01. For the correct execution of FRBACKUP CP(CP3) ..., another set of volumes in the new storage controller must be added to CPBSG1.

Figure 3-10 SMS constructs that span storage controllers

3.5.3 Extend and overflow storage group types

The extend and overflow storage group types that were introduced in z/OS V1.3 enable data sets to be allocated on or extended onto volumes that are not a part of a main source storage group.

Extended storage group

is a feature of the pool storage group type that is used for secondary allocation when the primary storage group has insufficient available space. Without this support, extended processing can select only volumes from within the same storage group as the initial allocation.

Overflow storage groups

are used for the initial data set creation when insufficient space is available in the primary storage group for the first extent of a data set. If an overflow storage group is defined and the ACS routines allow the use of the overflow storage group for this data set, a data set will be directed to the overflow storage group if all volumes in the primary storage groups are over their high allocation threshold.

Figure 3-9 on page 39 shows Overflow and Extend SG Name fields in the Pool Storage Group Alter panel.

If you list all of the storage groups, you will find that OVERFLOW in column 41 and Extend SG Name at column 42 contain valid values if you implemented SMS extended or overflow storage groups.

If you implemented SMS extended or overflow storage groups in your environment, you must ensure that all extended and overflow storage groups are included in the storage group list of the appropriate copy pools.

DS8000

DS8000

SG1 SG2 CPBSG3 CPBSG1 Rel at ed w ith -> Re la te d w ith -> CP3 Rel at ed w ith -> CPBSG2 SG3 CP01

DFSMS does not verify that extend and overflow storage groups that are associated with the main source storage groups are included in the copy pool definition. Source volumes that are contained in overflow and extend storage groups also require target volumes to be set aside for their use in the CPBSG. A backup of each volume is made whether or not it contains any data.

3.5.4 GRSplex

A resource will be obtained that prevents a copy pool from being processed by two separate tasks in the GRSplex:

QNAME ARCENQG

RNAME COPYPOOL&&cpname

SCOPE SYSTEMS

The scope of this resource extends beyond an HSMplex because a copy pool is defined at the SMSplex level, so we must prevent all DFSMShsm hosts, regardless of which HSMplex they reside in, from processing the same copy pool. This resource will be obtained by all functions that are processing a copy pool. The resource will be obtained unconditionally; that is, if the resource is not immediately available, the function will wait:

򐂰 The functions that will obtain this resource exclusively are FRBACKUP and FRDELETE.

򐂰 LIST, QUERY, and FRRECOV will obtain the resource as shared.

Before processing either a backup or recover of a volume, DFSMShsm serializes the source and target volumes to prevent concurrent DFSMShsm tasks in the HSMplex from processing the same volumes.

Another resource will be obtained for the dumping of copy pools:

QNAME ARCENQG

RNAME CPDUMP&&cpname&&V

nnn

SCOPE SYSTEMS

The

nnn

is the version that is being dumped. Only a single host can dump a particular disk version at a time.

3.5.5 Sysplex with multiple DFSMS levels

You can work with control data sets (CDS) that are shared across a sysplex. If different systems in the sysplex have different versions of DFSMS, certain features are not available to all systems. If you try to modify a control data set from a system that does not have the most current version of DFSMS that is used in the sysplex, you will see the panel that is shown in Figure 3-11 on page 43.

Important: Extend or overflow storage groups must be used only if all source storage

groups that use a particular extend or overflow storage group and the extend or overflow storage group are all contained within the same copy pool. Extend and overflow storage groups must not be used if the source storage groups that use them are contained within different copy pools.

Figure 3-11 Uplevel CDS warning

This message is merely a warning. You can change the default value N in the Perform Operation field to continue with your changes and modify the SCDS.

In document DFSMShsm Fast Replication Technical Guide (Page 57-61)