Virtual storage above and below 16MB line performance checklist

Note:

The lower the number of concurrent transactions in the system, the lower the usage of virtual storage. Therefore, improving transaction internal response time decreases virtual storage usage. Keeping programs in storage above the 16MB line, and minimizing physical I/Os makes the largest contribution to well-designed transaction internal response time improvement.

Item Topic
CICS® region
Increase CICS region size Increasing the CICS region size
Reorganize program layout within region Defining programs as resident, nonresident, or transient
Split the CICS region Splitting online systems: virtual storage
   
DSA sizes
Specify optimal size of the dynamic storage areas upper limits (DSALIM, EDSALIM) The dynamic storage areas
Adjust maximum tasks (MXT) Setting the maximum task specification (MXT)
Control certain tasks by transaction class Using transaction classes (MAXACTIVE) to control transactions
Put application programs above 16MB line Putting application programs above the 16MB line
   
Database considerations
Increase use of DBCTL and reduce use of shared database facility Setting DBCTL minimum threads (MINTHRD)
Replace DL/I function shipping with IMS™ DBCTL facility Setting DBCTL minimum threads (MINTHRD)
Review use of DB2® threads and buffers Tuning the CICS DB2 attachment facility: Introduction
   
Applications
Use PL/I shared library facility Using the PL/I shared library
   
Journaling
Increase activity keypoint frequency (AKPFREQ) value Setting the activity keypoint frequency (AKPFREQ)
   
Terminals, VTAM® and SNA
Reduce VTAM input message size Setting the size of receive-any input areas (RAMAX)
Reduce concurrent VTAM inputs Setting the size of the receive-any pool (RAPOOL)
Reduce terminal scan delay Adjusting the terminal scan delay (ICVTSD)
Discourage use of MSGINTEG and PROTECT Adjusting the number of transmissions in SNA transaction flows (MSGINTEG, and ONEWTE)
Reduce concurrent VTAM logon/logoffs Limiting the number of concurrent logon/logoff requests (OPNDLIM)
Reduce AIQMAX setting for autoinstall Tuning automatic installation of terminals
   
MRO/ISC considerations
Implement MVS™ cross-memory services with MRO CICS intercommunication facilities and performance: overview
Implement MVS cross-memory services with shared database programs CICS intercommunication facilities and performance: overview
   
SSL (Secure Sockets Layer)
Increase CICS region size Managing the performance of Secure Sockets Layer support
   
JVMs
Tune the JVM initialization options Java applications using a Java virtual machine (JVM): improving performance
   
Miscellaneous
Reduce use of aligned maps Choosing aligned or unaligned maps
Prioritize transactions Prioritizing tasks
Use only required CICS recovery facilities CICS recovery: performance considerations
Recycle job initiators with each CICS startup Using job initiators

Related tasks
Performance checklists
Input/output contention performance checklist
Real storage performance checklist
Processor cycles performance checklist
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