Virtual I/O storage space

Virtual I/O operations may send VIO dataset pages to the local paging dataset space. During a quick start, the installation uses the CVIO parameter to purge VIO dataset pages. During a warm start, the system can recover the VIO dataset pages from the paging space. If an installation wants to delete VIO page space reserved during the warm start, it issues the CVIO system parameter at the operator's console. CVIO applies only to the VIO dataset pages that are associated with journaled job classes. (The VIO journaling dataset contains entries for the VIO datasets associated with journaled job classes.) If there are no journaled job classes or no VIO journaling dataset, there is no recovery of VIO dataset pages. Instead, all VIO dataset pages are purged and the warm start is effectively a quick start.

If the SPACE parameter for a DD statement having a UNIT parameter, associated with a UNITNAME that was defined with having VIO=YES, is not specified, the default size is 10 primary and 50 secondary blocks with an average block length of 1000 bytes.

The cumulative number of page datasets must not exceed 256. This maximum number of 256 page data sets should follow these guidelines:

There must either be one PLPA page data set or *NONE* must be specified to indicate that SCM is to be substituted. In either case, the specification counts toward the 256 maximum.
There must either be one common page data set or *NONE* must be specified to indicate that SCM is to be substituted. In either case, the specification counts toward the 256 maximum.
There must be at least one local page data set, but no more than 253.

The actual number of pages required in paging data sets depends on the system load, including the size of the VIO data sets being created and the rates at which they are created and deleted.