# SMS Storage Class

The SMS Storage Class attributes provide information about the SMS storage classes that have been defined.

Availability: Specifies whether data set access should continue in the event of a single device failure. This determines whether the data set is placed on RAID or duplexed volumes.

Cache Set Name: Specifies a name that is associated with a coupling facility structure that is used for data sets that are defined for VSAM record level sharing.

Description: The description of this storage class as entered by a storage administrator.

Direct Bias: Bias determines which volumes MSR (millisecond response time) performance numbers (READ, WRITE, or BOTH) to consider during volume selection. If you specify a READ (R) bias, a cache storage control should be available to allow caching. If you specify a WRITE (W) bias, the DASD fast write feather of an IBM® 90 storage controller with cache should be available to allow the use of DASD fast write. If you do not specify a value for bias (BLANK), the MSR time determines whether caching or DASD fast write are used.

Direct MSR Objective: Specifies the desired millisecond response time for direct access I/O operations. This is used at allocation time to select a device capable of satisfying this objective.

Guaranteed Space: Specifies whether this storage class has the guaranteed space attribute. You can allocate space for single volume and multi-volume data sets by specifying a storage class with the guaranteed space attribute. The request fails when space is insufficient.

The guaranteed space attribute does not apply to objects, but it does apply to both VSAM and non-VSAM-managed data sets. For a multi-volume system-managed data set, primary space is preallocated on all volumes. The first volume becomes the primary volume. The remaining volumes become candidate volumes with preallocated space. When the primary extent on the current volume becomes full, VSAM attempts to create secondary extents on the current volume. If there is not enough space left on the current volume, VSAM uses the preallocated primary extent on the next volume. The next volume is converted from a candidate volume to a primary volume.

Guaranteed Synchronous Writes: Specifies whether guaranteed synchronous write is defined for this storage class. Ensures that data transfer occurs and is complete between the channel and the device when write operations are issued to a PDS.

Last Update User ID: The last user ID to update this storage class definition.

Last Updated: The date and time the storage class definition was last updated.

Managed System: The SMS name of this system.

Sequential Bias: Bias determines which volumes MSR (millisecond response time) performance numbers to consider during the volume selection. Values are READ WRITE, or BOTH.

Sequential MSR Objective: Specifies the desired millisecond response time for sequential access I/O operations. This is used at allocation time to select a device capable of satisfying this objective.

Storage Class Name: The name that identifies this storage class.