vsam cardinal

VSAM Cardinal

VSAM Cardinal Abstract This presentation addresses issues relevant to all z/OS enterprises that exploit VSAM. When the issues addressed by this presentation are ignored, unintentionally overlooked, or put on the back burner for higher priority tasks, both application- and system-level performance will suffer. The intent is to provide you with a systematic and automated approach to creating and maintaining high levels of integrity, productivity, and performance in your VSAM environment.

VSAM Cardinal Abstract, cont.

We will discuss how VSAM natively controls sharing of datasets and the impact on application performance, availability, and integrity of the underlying data. We will also address the challenges associated with establishing and maintaining a high-performance VSAM environment without having a negative impact on the productivity of the IT staff.

VSAM Sharing and Integrity • Challenge

ü VSAM allows only one program to update a dataset (with full integrity) §  Can cause long batch cycles §  Reduces the availability of online systems

– Manipulation of the SHAREOPTIONS parameter » Further reduces online availability » Negative impact on application performance

VSAM Sharing and Integrity • Band-Aids

ü Re-develop applications using a proprietary DBMS

ü Develop CICS transactions that perform batch functions

ü Create shadow databases ü Make batch programs open and close files ü Homegrown software for remote file access

(function shipping?)

VSAM Sharing and Integrity • Band-Aids

ü Manipulation of the SHAREOPTIONS parameter § Further reduces online availability § Negative impact on application performance § Four specific options with various levels of access and integrity

VSAM Sharing and Integrity • SHAREOPTION 1

ü Any number of OPENs for batch or online ü These OPENs must be read-only ü Only one program (or transaction) can open

for UPDATE (write) ü Provides complete integrity

VSAM Sharing and Integrity • SHAREOPTION 2

ü Any number of OPENs for batch or online ü These OPENs must be read only ü Only one program (or transaction) can open

for UPDATE (write) ü VSAM locks the CI, but users will have to

ENQ on the record key for integrity

VSAM Sharing and Integrity • SHAREOPTION 3

ü Completely shareable by anybody and everybody

ü Integrity? ü SHAREOPTION 3 applies to both cross-

region and cross-system integrity

VSAM Sharing and Integrity • SHAREOPTION 4

ü Completely shareable by everybody (READ and UPDATE)

ü SHAREOPTION 3 level integrity, use ENQ/DEQ for each I/O operation

ü SHAREOPTION 4 applies to both cross- region and cross-system integrity

VSAM Sharing and Integrity • Band-Aids

ü Locking § RLS could be used

– Enables CICS to do all writes – This might allow for reads – Read integrity is not guaranteed

» So again, user, do your own ENQs

VSAM Sharing and Integrity •  The optimal approach

ü Control VSAM sharing with a transparent Intelligent File Management System (IFMS) § Intercepts, controls, and executes batch and online I/O requests § Could run in its own address space § Functions as the VSAM traffic cop with full data integrity

– Not limited by number of read/update users

IFMS in the Environment CICS

IFMS PGM A PGM  B  

VSAM

IFMS in the Environment • Capitalizes on CICS’s multi-programming capabilities

• Transparently intercepts VSAM requests for files and performs I/O operations with integrity (batch and online)

• Two methods of communication ü LU 6.2 for remote file access ü XMS if both the batch job and CICS are

running on the same CPU

IFMS Environment

BATCH

Application Program

with IFMS Intercept

IFMS I/O

Manager and Online Interfaces

VTAM LU6.2

CICS

MVS Cross Memory Services

IFMS in the Environment • Complete data integrity

ü I/O is centralized within CICS ü Both CICS and batch jobs can update the

same file simultaneously • Total transparency

ü No programming changes ü No new interfaces to learn

• Selective SYNCpointing and Recovery (SSAR)

IFMS in the Environment • Control and flexibility

ü  You define which jobs are impacted §  You determine max number of jobs that may

simultaneously access CICS

ü  Works within your security environment ü  Dynamically suspend, restart, cancel, or

change the number of I/Os being sent to CICS by a given job

Primary Menu Screen

Selected Dataset Screen

Job Maintenance Screen

Job History Screen

Selected DDNAME Screen

Selected DDNAME Screen

IFMS in the Environment • Selective SYNCpointing and Recovery (SSAR) ü Tier 1 ü Tier 2 ü Tier 3

IFMS with SSAR • Needless to say, Tier 1 is the simplest to implement and is mostly suited for short-running jobs that do few updates. Tier 1 relies on CICS DTB for recovery.Tier 2 is straight forward, as well, but will need a basic understanding of journaling. Tier 3 will need some attention

IFMS with SSAR • The SYNC level field on the JOB MAINTENANCE screen identifies journaling (Tier 2) and is the number of CICS file ENQUEUEs allowed before a SYNCpoint is issued

IFMS with SSAR • With Tier 1 or 3, 0 (zero) is used • With Tier 2, CICS does not journal

ü Journaling is from within the IFMS

• Journaling is completely transparent to the application

IFMS with SSAR • Recovery (in Tier 2) is started using the journal

CICS

VSAM Files

Program A IFMS

Program B IFMS

IFMS

“A” Files

“B” Files

Journal

IFMS with SSAR • Unlike the prior two options, Tier 3 will require program modifications

• Tier 3 is best suited for long-running jobs

IFMS Solution Summary • Unlimited sharing with integrity

ü Total transparency ü No source code modifications

§  No recompiling of current code

ü No mods to existing system software ü No proprietary address spaces to support ü Support for all programming languages ü No new interfaces or commands to learn ü Easy installation, activation/deactivation

What about VSAM Performance? • VSAM is the most widely used access method in one form or another ü Dwindling amount of mainframe tuning expertise ü When properly tuned─very strong performer ü Without proper tuning

§ Online and batch performance suffers § Can lead to unnecessary processor and DASD

upgrades § Lost productivity performing file reorgs

What about VSAM Performance? • Improving VSAM performance

ü Identify obvious waste and inefficiencies § Run a FREECYLINDERS report § Run an EMPTY report § Run a “Not Updated Since 20xx” report

ü Analyzing the remaining legitimate datasets § Get professional help!

– Find a software solution that streamlines the process of analyzing and managing VSAM

» Design and allocate » Analyze » Reporting

MENU

Dataset Design

Dataset Design Profile

Search and List Capabilities

Background/Foreground Analysis

Batch Analysis

Foreground Analysis

Profile Update Menu

Analysis Reporting Options

Background Job Profile

Extended List Catalog

Dataset Recommendations Profile

VSAM Performance Summary

• VSAM tuning is critical ü Limited human resources are available

• A good software solution will support the major components of your VSAM environment ü Design/Allocate ü Analysis ü Recommendations

VSAM Performance Summary ü Reporting ü Reduce/eliminate unnecessary reorgs

• Reduced operational costs for DASD • Model and design VSAM files based on current or modified definitions

• ISPF interface for quick ad hoc changes