VTOC Validation Tool
Publication Date: 2016-Oct-28
The IP.com Prior Art Database
Disclosed is a Volume Table of Contents (VTOC) validation tool for the z/OS operating system that enables the diagnosis of errors within the VTOC and/or Index. This further enables repairs to the VTOC and/or index structures so that the structures do not become disabled as well as the rapid diagnosis of the structural errors that prevent the rebuilding of the VTOC and/or Index.
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VTOC Validation Tool
All Direct Access Storage Devices (DASD) have a volume map that is used by the operating system to manage user data and free space on the device. In the z/OS operating system, this map is called the Volume Table of Contents (VTOC). User data on a volume is kept in data sets and pointers to these data sets are maintained within Data Set Control Block (DSCB) records in the VTOC. In most cases, the volume also has a VTOC index data set that has pointers to data set DSCB records in the VTOC. This VTOC may be in one of two states. One is the OSVTOC state, in which the free space is mapped by free space DSCB records within the VTOC. The other state is the Indexed VTOC, in which the VTOC Index data set manages the allocation of space on the volume.
In the evolving world where DASD volumes are getting bigger with larger capacities and businesses are seeing very strict service level agreements, it is imperative that DASD access be as quick as possible. There are situations that can cause the VTOC index to be disabled by CVAF and when this occurs, clients may see very poor execution time for various jobs
when accessing the volume(s) affected. In general, determining the cause is related to the VTOCIX being disabled is a time-consuming process. As a VTOCIX is not a requirement, it makes sense that the index should not be disabled if the problem can be determined and the index rebuilt. If the index cannot be rebuilt, then it is also imperative to quickly diagnose the reason. This also holds true for the VTOC structure, in that errors within this structure can lead to data sets not being accessible, or new data sets not being able to be created.
The novel contribution is a VTOC validation tool that enables the diagnosis of errors within the VTOC and/or Index, to further enable:
• Repairs to the VTOC and/or index structures so that the structures do not become disabled
• Rapid diagnosis of the structural errors that prevent the rebuilding of the VTOC and/or Index
The VALIDATE tool validates the structure of the VTOC and/or Index, and either fixes the structural errors or reports the errors preventing the rebuild. The...