Migrating to z/OS Version 1 Release 4

This topic provides information that you need to consider before migrating your z/OS® system to use DFSMStvs and describes migration tasks. For more information on migrating DFSMS to z/OS Version 1 Release 4, see z/OS Migration.

DFSMStvs enables you to run batch VSAM processing concurrently with CICS® online transactions. You can run multiple batch jobs and online transactions against the same VSAM data, in data sets defined as recoverable, with concurrent updates. DFSMStvs offers these features:

Concurrent shared update of VSAM recoverable data sets across CICS transactions and batch applications
Ability to run multiple batch jobs concurrently instead of serially
Logging, commit, and backout functions
24 x 7 CICS Transaction Server (TS) applications
Data sharing across CICS TS applications, batch applications, and local or distributed object-oriented (OO) applications

Building on the functionality of VSAM RLS, DFSMStvs provides transactional capability within the file system. If a batch job fails during concurrent shared updates of recoverable VSAM data sets, DFSMStvs provides the services to back out any changes that the batch job made automatically, restoring the data to the state it was in at the last synchronization point (commit or back out).

You can use DFSMStvs in two major areas:

Transactional processing provides data sharing for recoverable resources. Transactional processing ensures that the data is kept in sync while multiple parties update the data and ensures data integrity in the event of a job or system failure. Products such as CICS, IMS™, and DB2® provide a transactional environment.
Transactional recovery isolates the changes made to recoverable resources into logical units of work that are recoverable. When a transaction makes a change, only that transaction can update the changed data. After DFSMStvs commits the transaction, all data associated with that logical unit of work is available to other transactions for update.

DFSMStvs also supports forward recovery logging for data sets that are defined as forward recoverable (the LOG parameter value is ALL). If data is lost or damaged, you can restore it from a backup, and you can use a forward recovery utility such as CICS VSAM Recovery (CICSVR) to reapply changes that were made since the last backup.

CICSVR automates the recovery of lost or damaged VSAM data sets. It determines what CICS journals and VSAM backups are needed, and it constructs the recovery jobs. CICSVR provides automated complete recovery, forward recovery, and backout functions. CICSVR VSAM batch logging is available with CICS VSAM Recovery V3R1. For more information about CICSVR, see the CICS Transaction Server for z/OS Information Center at http://publib.boulder.ibm.com/infocenter/cicsts/v3r1/index.jsp .

Implementing DFSMStvs could affect the following areas of your processing environment.

Area	Considerations
System customization	Updated IGDSMSxx member of SYS1.PARMLIB DFSMStvs log stream definitions and initialization parameters
Storage administration	DFSMSdfp: New DFSMStvs parameters in the IGDSMSxx member of SYS1.PARMLIB and in the MVS™ SET SMS, VARY SMS, and SETSMS commands DFSMSdss: Data sets designated by DFSMStvs as eligible for backup-while-open processing
Operations	None
Auditing	None
Magnetic tapes	Block sizes of up to 262␠144 bytes
Application development	Job control language (JCL) statements: You can specify the RLS parameter with the CRE (consistent read explicit) subparameter. Access method services: The ALLOCATE, ALTER, DEFINE ALTERNATEINDEX, DEFINE CLUSTER, and DEFINE PATH commands have been updated for DFSMStvs. Macros: The ACB, GENCB, GET UPD, IDALKADD, RPL, POINT, and PUT UPD macros have been updated for DFSMStvs.
Messages and codes	Many MVS system messages have been added or changed for DFSMStvs, including new routing and descriptor codes. For descriptions of these messages and codes, see z/OS MVS System Messages, Vol 6 (GOS-IEA), z/OS MVS System Messages, Vol 8 (IEF-IGD), and z/OS MVS System Messages, Vol 9 (IGF-IWM).
General use	Before using DFSMStvs, evaluate which applications are good candidates and which applications cannot support the necessary changes.