Steps for providing a SnapShot working-space data space

Perform the following steps to provide a SnapShot working-space data space:

Ensure that adequate space is available before using the CONCURRENT keyword on DFSMSdss commands that refer to data sets on an RVA subsystem. The virtual-concurrent-copy SnapShot function requires some dedicated space on one or more volumes in the same RVA subsystem as the source data set. Provide the necessary space by allocating dedicated data sets, called working-space data sets, with the following naming convention:
```
SYS1.ANTMAIN.Ssysname.SNAPnnnn
```
Variable sysname is the system identifier, and nnnn is a four-digit decimal number in the value range 0001–9999. If the system identifier is eight characters, ‘S’ replaces the first character.
Ensure that you catalog the working-space data sets. DFSMSdss performs a numerically-sequential catalog search for each data set, starting with SYS1.ANTMAIN.Ssysname.SNAP0001, until it encounters a catalog locate error. A catalog locate error indicates that DFSMSdss could not find the data set. DFSMSdss cannot use data sets as working space that are beyond the data set that DFSMSdss was unable to find.
Allocate the working-space data sets as physical sequential, nonextended-format data sets. The data sets can be SMS-managed or non-SMS-managed. If the catalog search for a working-space data set indicates that the data set is multivolume, DFSMSdss will not use it as a working-space data set.
Extend the data set by filling it with data before starting the DFSMSdss job if you want to allocate secondary space. The system data mover (SDM) does not extend a working-space data set. SDM holds an enqueue for the data set while the working space is being used during a SnapShot copy operation. It then releases the enqueue after all usage of the data set is completed. You can reallocate or extend a working-space data set when SDM does not have the data set enqueued. SDM uses the new size of the data set. You can add additional working-space data sets after ANTMAIN has completed the initialization process.
SDM uses these data sets the first time an out-of-working-space condition is encountered during a SnapShot copy operation. When this condition occurs, SDM refreshes the list of working-space data sets by performing a catalog search that starts with SYS1.ANTMAIN.Ssysname.SNAP0001.
The LRECL and block size can be any valid combination. The system uses the tracks within the data set as the target of SnapShot copy operations. Therefore, do not try to access these tracks with normal data access methods.

Recommendation: It is recommended that you protect the working-space data sets by security, such as RACF®, to ensure that unauthorized users do not have access to sensitive data.
Allocate data sets on a volume in each RVA subsystem that you have set aside for virtual-concurrent-copy SnapShot. If the RVA subsystem has more than one defined device type, you must allocate a working-space data set on each device type that contains a data set that DFSMSdss SnapShot copy will process. Device types are, for example, 3390 and 3380. Different models within each device type do not require separate working-space data sets.
More than one system can simultaneously access data on the same RVA subsystem. If each system has DFSMSdss jobs that specify CONCURRENT, then each system requires at least one working-space data set.

Example: DFSMSdss must allocate three working-space data sets to process data on an RVA subsystem from three MVS systems. The working-space data sets must include at least one of each device type that contains data that SnapShot will process.

If there is insufficient working space, the SnapShot initialization for one or more data sets in the job fails. To avoid this, determine the largest total amount of data that you plan to process in a single DFSMSdss COPY or DUMP command on that RVA. The total size of all working-space data sets that you have allocated on each RVA subsystem should equal or exceed the determined amount of space.

Note: Do not place any working-space data set on a PPRC primary volume.