Although much of the coding of a VS COBOL II program will be the same when running under IMS, you should be aware of the following recommendations and restrictions.
Recommended Compiler Options
It is recommended that the RENT and RES compiler options be used for optimum performance in the IMS environment. By using these options, you can preload programs and library routines. IMS allows COBOL programs to be preloaded, that is, to remain resident in storage. This can boost performance, since subsequent requests for the program can be handled faster when the program is already inside the processor (rather than fetched from a library each time it is needed).
VS COBOL II allows programs to be preloaded or not with the same set of compiler options, namely the RENT and RES options. A program that is to be used in both apreloaded and a non-preloaded way (or used preloaded exclusively) must be reentrant and use the COBOL Library Management Facility. In addition, the RES option provides you with the opportunity to tune the VS COBOL II system for better performance.
Running Above the 16-Megabyte Line
To run above the 16-megabyte line, your application program must be compiled with RENT, RES and either DATA(24) or DATA(31), depending on your IMS environment. If you are using a release of IMS prior to IMS/ESA Version 3, the data for IMS application programs must reside below the 16-megabyte line, and you must specify DATA(24) to use IMS services. DATA (24) ensures that all COBOL data areas are below the 16-megabyte line and will be addressable to programs in 24-bit addressing mode.
With IMS/ESA Version 3 and later, the data for IMS application programs can reside above the 16-megabyte line, and you can specify DATA (31) for programs that use IMS services. DATA (31) enables you to use the full 31-bit addressing capabilities of MVS/XA or MVS/ESA.
Recommended Link-Edit Attributes
The link-edit attributes recommended for proper execution of VS COBOL II programs under IMS are:
Non-IMS I/O statements must not be used in IMS VS COBOL II Message Processing Programs (MPPs). For example, the following are not allowed:
In addition to the above, ACCEPT, DISPLAY, RECEIVE, SEND, and STOP RUN statements are not allowed in IMS OS/VS COBOL programs.
Mixed VS COBOL II and OS/VS COBOL Applications
In a mixed VS COBOL II and OS/VS COBOL application, it is recommended that the LIBKEEP=YES run-time option be specified, the RENT/RES compiler options be used for VS COBOL II programs, and the RES/NOENDJOB be used for OS/VS COBOL programs. This allows OS/VS COBOL programs to be preloaded or not. If LIBKEEP=NO (which is the default), preloaded OS/VS COBOL programs must have been compiled with NOENDJOB.
If you preload the ILBOCOM library routine, then you must also preload these library routines:
The OS/VS COBOL NOENDJOB/ENDJOB compiler option produces different results when running with the VS COBOL II library than when running with the OS/VS COBOL library. In a VS COBOL II run-time environment:
A program remains in last-used state between COBOL transactions only when all the following conditions are true:
If OS/VS COBOL programs using NORES/NOENDJOB are to be used, then the library routine ILBONTR must be preloaded.
In an MVS/XA or MVS/ESA environment, the OS/VS COBOL application programs and the ILBO library routines run below the 16-megabyte line. Dynamic CALLs should be used to communicate between VS COBOL II programs above 16 megabytes and OS/VS COBOL programs below 16 megabytes.
The OS/VS COBOL user will experience performance differences when executing in the VS COBOL II environment (using VS COBOL II run-time libraries). VS COBOL II reconstructs the COBOL environment each time the IMS application main COBOL program is entered.
Each time an application main COBOL program is entered and exited, you incur overhead from the initialization and termination of the COBOL environment. It is recommended that the following VS COBOL II library routines be preloaded to enhance performance:
For performance reasons, if the RES or DYNAM option is used for OS/VS COBOL programs, the OS/VS COBOL compatibility library routines that are called should be preloaded.
IBM Mainframe Related Interview Questions
|IBM Lotus Notes Interview Questions||IBM-CICS Interview Questions|
|COBOL Interview Questions||Linux Interview Questions|
|IBM-JCL Interview Questions||IBM Mainframe Interview Questions|
|IBM AIX Interview Questions||IBM WAS Administration Interview Questions|
|IBM Lotus Domino Interview Questions||IBM Integration Bus Interview Questions|
|Mainframe DB2 Interview Questions||Unix Production Support Interview Questions|
Ibm Mainframe Tutorial
Introduction To Software Development
Introduction To Ibm Mainframes
Tso And Ispf
Jes2, ]es3 And Sms
Introduction To Job Control Language (jcl)
The Job Statement
The Exec Statement
The Job And Exec Statements
The Dd Statement
Procedures And Symbolic Parameters
Generation Data Groups (gdg), Compile/link-edit And Run Jcls
Access Method Services (ams)
Additional Vsam Commands
Introduction To Rexx
Overview Of Rexx
Introduction To Cics
Exception Handling In Cics
Developing A Cics Application
Cics Programming Techniques
Basic Mapping Support (bms)
Transient Data Control
Temporary Storage Control
Interval And Task Control
Cics Application Design
Recovery And Restart
System Security And Intersystem Communication
Cics Debugging Facilities And Techniques
Bms Map Definition Macros And Copylib Members
Cics Response And Abend Codes
Data, Information And Information Processing
Introduction To Database Management Systems
Introduction To Relational Database Management Systems
Database Architecture And Data Modeling
Overview Of Db2
Structured Query Language (sql)
Data Security And Access
Db2 Application Development
Qmf And Db2i
Db2 Performance Monitoring, Utilities And Recovery/restart
Overview Of Information Management System (ims)
Introduction To Vs Cobol Ii
Overview Of Application Development In Vs Cobol Ii
Overview Of The Cobol Program
Sorting And Merging Files
Coding Cobol Programs That Run Under Cics. Ims, Db2 And Ispf
Compiling The Program
Link-editing The Program
Executing The Program
Improving Program Performance
All rights reserved © 2018 Wisdom IT Services India Pvt. Ltd
Wisdomjobs.com is one of the best job search sites in India.