ABCs of z/OS System Programming Volume 3 - IBM Redbooks

1.7 DFSMStvs component
Provide transactional recovery within VSAM
RLS allows batch sharing of recoverable data sets
for read
RLS provides locking and buffer coherency
CICS provides logging and two-phase commit
protocols
Transactional VSAM allows batch sharing of
recoverable data sets for update
Logging provided using the System Logger
Two-phase commit and backout using Recoverable
Resource Management Services (RRMS)
Figure 1-7 DFSMStvs functions
DFSMStvs component
DFSMS Transactional VSAM Services (DFSMStvs) allows you to share VSAM data sets
across CICS, batch, and object-oriented applications on z/OS or distributed systems.
DFSMStvs enables concurrent shared updates of recoverable VSAM data sets by CICS
transactions and multiple batch applications. DFSMStvs enables 24-hour availability of CICS
and batch applications.
VSAM record-level sharing (RLS)
With VSAM RLS, multiple CICS systems can directly access a shared VSAM data set,
eliminating the need to ship functions between the application-owning regions and file-owning
regions. CICS provides the logging, commit, and backout functions for VSAM recoverable
data sets. VSAM RLS provides record-level serialization and cross-system caching. CICSVR
provides a forward recovery utility.
DFSMStvs is built on top of VSAM record-level sharing (RLS), which permits sharing of
recoverable VSAM data sets at the record level. Different applications often need to share
VSAM data sets. Sometimes the applications need only to read the data set. Sometimes an
application needs to update a data set while other applications are reading it. The most
complex case of sharing a VSAM data set is when multiple applications need to update the
data set and all require complete data integrity.
Transaction processing provides functions that coordinate work flow and the processing of
individual tasks for the same data sets. VSAM record-level sharing and DFSMStvs provide
Chapter 1. DFSMS introduction 13