The concurrent copy (CC) support for the 3990 Model 6 Storage Control uses z/OS® data spaces to contain track image copies of the data being processed by the DFSMSdss. The data spaces are backed by expanded storage and local paging spaces. The amount of expanded storage and local paging space required for CC usage is dependent on a number of variables. Based on simulations and test scenarios, a typical data space size is about 10% of the amount of data being dumped or copied with CC.

If your data space size exceeds this nominal value, you may need to consider the following planning guidelines for determining how much expanded storage or local paging space may be required for the following CC functions:

• Full volume and tracks copy; and full volume, tracks and physical data set dump operations:

  All volumes are processed on a track-by-track basis by DFSMSdss. The data space requirements can vary from 0% for a volume that has no updates during the DFSMSdss operation to 100% if the entire volume is updated before DFSMSdss can process it. For example, a 3390–3 that is 80% full (2671 cylinders) may require up to 2671 cylinders of data space storage if the volume is completely rewritten before DFSMSdss can process it. An example of this situation would be that a volume contains many VSAM data sets and a reorganization is done for all of the VSAM data sets on the volume while the CC job is being run for the volume.

• Logical data set copy and dump processing of non-VSAM data sets and nonindexed VSAM data sets (for example, VSAM ESDS), logical data set copy of indexed VSAM data sets (for example, VSAM KSDS), and logical data set dump of indexed VSAM data sets processed with NOVALIDATE are described as follows:

  These data sets are processed on a track-by-track basis by DFSMSdss. The data space is used to contain updates for tracks that have not yet been processed by DFSMSdss. The data space requirements can vary from 0% for a data set that has no updates during the DFSMSdss operation to 100% if the entire data set is updated before DFSMSdss can process it. For example, a 50-cylinder data set may require up to 50 cylinders of data space storage if the data set is completely rewritten before DFSMSdss can process it.

• Logical data set dump of indexed VSAM data set (for example, VSAM KSDS) processed with VALIDATE is described below:

  These data sets are processed with numerous accesses to sequence set information in the index component and track-by-track accesses to the data component. In all cases, update activity to either the data component or the index component maintains a copy of the updated track in the data space until the track is either processed by DFSMSdss or the dump operation is ended for all data sets.

  Index component tracks that do not contain sequence set information and data component tracks that are beyond the high used relative byte address are included in the CC operation but are never read by DFSMSdss. If those tracks are updated, they will remain in the data space for the duration of the dump operation for all data sets. If the data set has the sequence set information imbedded in the data component (using the IMBED attribute), no additional (nonupdated) tracks are maintained in the data space. If the data set has the sequence set information in the index component, then all index component tracks containing sequence set information will be maintained in the data space (whether they were updated or not) for the duration of the dump processing for the data set. For example, if the index for a VSAM data set is 20 cylinders and the data is 2500 cylinders, plan paging space of 20 cylinders for the index component.

  Based on the update activity during the dump operation, plan to use a paging space of between 0 and 2500 cylinders for the data. The most data space is used when doing a complete reorganization while dumping the VSAM data set. This requires 2520 cylinders of space. If only 10% of the data will change during the operation, you will need 20 cylinders for the index and 250 cylinders for the data or 270 cylinders of paging space.

In using CC against aggregate groups, determine the data space storage requirements based on the expected update rate to the data sets during the dump operations. Failure to allocate sufficient local paging space may result in system failures due to insufficient paging storage.