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Selecting Data Storage Volumes for Data Sets

IP.com Disclosure Number: IPCOM000050384D
Original Publication Date: 1982-Oct-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Duvall, KE: AUTHOR

Abstract

A computer managing data storage volumes of a storage system enhances space allocation for data sets in a manner which provides maximum, feasible use of available space within a group of general use data storage volumes. In particular, the probability of almost immediate reuse of free data storage space is enhanced for temporary data set allocations. A group of such storage volumes may be defined as being exhausted of usable space if the total volume free space is reduced to zero cylinders (though actual tracks may not be utilized). Available or free space is measured in all currently mounted or active volumes which are eligible for selection for allocation. Eligibility is determined by a comparison of the space requirements of the data set and space availability and volume usability of various unmounted and active volumes.

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Selecting Data Storage Volumes for Data Sets

A computer managing data storage volumes of a storage system enhances space allocation for data sets in a manner which provides maximum, feasible use of available space within a group of general use data storage volumes. In particular, the probability of almost immediate reuse of free data storage space is enhanced for temporary data set allocations. A group of such storage volumes may be defined as being exhausted of usable space if the total volume free space is reduced to zero cylinders (though actual tracks may not be utilized). Available or free space is measured in all currently mounted or active volumes which are eligible for selection for allocation. Eligibility is determined by a comparison of the space requirements of the data set and space availability and volume usability of various unmounted and active volumes. Space measurement is based upon periodic but individual job independent space and usability measurement. Available space on unmounted volumes or volumes mounted to another host is indirectly measured (from information retained in a system controlled data set).

Data storage systems define available data storage space in terms of storage volumes. For DASD (direct access storage device), such volumes can be physical volumes, i.e., actual disk storage spindles or virtual volumes. Virtual volumes can be accessed on various DASD types and may reside in a data storage subsystem having an automatic tape library with a DASD data buffer. Each virtual volume has a standard or indexed table of contents termed "VTOC", which defines the current attributes and parameters of (parms) the vir...