VATLSTxx contains one or more volume attribute lists that predefine the mount and use attributes of direct access volumes. The mount attribute determines the conditions under which a volume can be demounted. The use attribute controls the type of requests for which a volume can be allocated.
The system programmer can predefine volume “mount” attributes as permanently resident or reserved, and can predefine volume “use” attributes as storage, public, or private. Therefore, critical direct access volumes can be controlled because the “mount” and “use” attributes determine the type of data sets that can be placed on a volume. During allocation, data sets on volumes marked permanently resident or reserved are selected first because they require no serialization, thus minimizing processing time.
You can ensure a faster initialization by specifying the volume attribute list(s) efficiently. Do not, for example, specify a list at a given IPL that contains entries for volumes that will not be mounted. Un-mounted volumes require operator intervention with resultant delay.
There are two ways to define the use and mount attributes for DASD volumes. You can define them in individual entries in the VATLSTxx member, one volume to each entry, or you can use one entry to define a group of volumes. In this second way, you specify generic volume serial numbers and device types for groups of volumes.
Specifying generic values makes it easier for you to maintain your VATLSTxx members. Give one generic name to a group of volumes mounted on devices that have the same device type and the same mount and use attributes. Specify an asterisk (“*”) for the device type when groups of volumes have the same volume serial numbers, mount attributes, and use attributes, regardless of the devices the volumes are mounted on. See Specifying a generic volume serial number and Specifying a generic device type for more information.
For JES3, DEVICE and SETRES initialization statements, rather than the VATLST, can be used to specify permanently-resident volumes. In a JES3 complex, you must assign the same mount attribute to a volume mounted on every system in the complex. For example, if you use the mount attribute of “permanently resident” for the system residence volume on one system, you must use the same use attribute on all the other systems.
If VATLST members are used for volumes resident on devices that are shared among multiple systems, the mount attributes for a specific volume must be the same on all systems.