Legacy Systems
Transforming Mainframe Applications
  Table of Contents  v-16.01.01 - l2ntech1.htm 
  Introduction
  The Target Environment
  The Current Environment
  Possibilities and Requirements
  Mainframe Screens, Convert to HTML
  Combine & Change Screens, Application Code Changes
  New Presentation Logic & Access to Application Server Data
  Segment the Application & Distribute the Business Logic
  Additional Topics
  Centralized or Distributed
  Pre-defined or Event-Driven Processes
  Transform, Terminal to Logic Based Sessions
  The EBCDIC and ASCII Environments
  JAVA Script to Complement HTML
  The Mainframe Connection
  Access to Data or Sharing of Data
  Access to Process or Sharing of Process
  Immediate Processing
  Deferred Processing or Shifting of Processing
  Questions
  Summary
  Software Agreement and Disclaimer
  Downloads and Links
  Current Server or Internet Access
  Internet Access Required
  Glossary of Terms
  Comments or Feedback
  Company Overview
The SimoTime Home Page 

Table of Contents Previous Section Next Section Introduction

Today, many companies are facing the competitive pressures of providing and gathering information via the Internet. The business of doing business via the Internet has moved to the forefront. Quite often this will require access to data and the coordination with processes of existing systems and business applications. These companies have mainframes running large CICS or IMS applications delivering computerized business functions throughout their enterprise.

These companies would prefer not to make any changes to the mainframe application code and just have things magically work in the Internet environment. However, with current emulation or migration technologies, skills disparity and application design this is impractical for all but the simplest of mainframe applications. Customers are now looking at ways to minimize this effort and accelerate the process of moving to the Internet. This will require a cooperative effort of Internet and Mainframe resources.

Let's take a minute to review the business objectives for extending mainframe legacy applications to the Internet.

1. Use Internet technologies as the delivery vehicle for the profitable exchange of business information.
2. Improve the Level-of-Service to existing customers.
3. Access a wider audience of potential customers.

Please note that many of the items discussed in this document are based on the hardware and software technologies that were available when this document was created. This is a rapidly changing environment and functional improvements are expected. The intent of this document is to provide readers with various alternatives and possible issues when extending mainframe legacy applications to the Internet.


We have made a significant effort to ensure the documents and software technologies are correct and accurate. We reserve the right to make changes without notice at any time. The function delivered in this version is based upon the enhancement requests from a specific group of users. The intent is to provide changes as the need arises and in a timeframe that is dependent upon the availability of resources.

Copyright © 1987-2019
SimoTime Technologies and Services
All Rights Reserved

Table of Contents Previous Section Next Section The Target Environment

The goal is to use the Internet to deliver new or existing business functions. This may be within an enterprise via an Intranet or extended directly to the customers of an enterprise via the World Wide Web.

       
Layer-1
Mainframe
 
DB2 VSAM IMS
MVS
Connectivity Services
 
Layer-2
Transport
 
 
 
Layer-3
Servers
 
Connectivity Services
Oracle Data Base U N I X
Application Server
Browser Interface
 
Connectivity Services
  Windows   Server Data Base
Application Server
Browser Interface
 
Layer-4
Transport
 
   
 
   
 
Layer-5
Browsers
 
Browser
Windows
 
Browser
Windows
 
Browser
Windows
 
Browser
Windows
 
Browser
Windows
 
Browser
Windows
 
       
Figure 1, Target Environment for Extending Legacy Applications to the Internet

Layer 1 in the preceding figure shows an example of a possible mainframe that has been configured to handle incoming request from intelligent workstations or application servers.

Layer 2 is rapidly becoming a TCP/IP connection instead of an LU-6.2 connection. In recent years more and more companies have added TCP/IP networks to their mainframes.

Layer 3 shows an example of two application server machines. Notice the possible local data bases and the connection between the two application servers. This connection between the application servers make it possible for a windows client running standard browser technology to connect to the application server for NT to access its data base or have the request routed to the application sever for UNIX to access its data base or routed on to the mainframe for processing.

Layer 4 shows the connection between the application server machines and the Windows client machines. This connection is a standard RAS connection using TCP/IP.

Layer 5 shows the client machines running Windows/98/NT/2000 with Internet Explorer or Netscape.

Table of Contents Previous Section Next Section The Current Environment

The current environment may be a CICS or IMS application sending screen images then receiving keyboard responses to and from a fixed function terminal. The terminals are usually 3270's with the screen images being 3270 formats created from BMS (Basic Mapping Services) source members for CICS and MFS (Message Formatting Services) source members for IMS.

       
Layer-1
Mainframe
 
DB2 VSAM IMS
MVS
VTAM
 
Layer-2
Transport
 
 
 
Layer-3
Controllers
 
3270 Controller
 
3270 Controller
 
Layer-4
Transport
 
   
 
   
 
Layer-5
Terminals
 
3270
Terminal
 
3270
Terminal
 
3270
Terminal
 
3270
Terminal
 
3270
Terminal
 
3270
Terminal
 
       
Figure 2, Current Environment for Delivering Information within an Enterprise

Layer 1 in the preceding figure shows an example of a possible mainframe that has been configured to handle requests from "fixed function", 3270 terminals. I have not used the term "dumb terminal" for a reason. Many ASCII terminals were dumb terminals that simply scrolled a string of text from left-to-right, top-to-bottom. The 3270 terminals have quite a bit of functionality built into the hardware.

Layer 2 is usually an SSCP-PU connection. In recent years many companies have added TCP/IP networks to their mainframes.

Layer 3 shows an example of two 3270 controllers.

Layer 4 shows the connection between the 3270 controllers and the 3270 terminals. This is usually an LU-2 connection.

Layer 5 shows the 3270 terminals. Normally, these are devices that support screens of 24 lines of 80 characters. Some customers run 3270, model 5 machines that allow more lines and columns. For example, a mod-5 could display 36 lines of 132 characters.

Table of Contents Previous Section Next Section Possibilities and Requirements

No single WEBerization process is suitable for all situations. Companies need to determine the most appropriate process (or variety of processes) based on the company's business requirements, staff competencies and current application constraints.

Let's take a look at a few of the possible approaches for WEBerizing a Legacy application.

1. Mainframe Screen Conversions to HTML with minimum changes to the application code.
2. Consolidate and Change screens, make minimum changes to the presentation logic.
3. Construct new presentation logic and begin to separate from the business logic.
4. Segment the application and distribute components to application server machines.
5. Additional Topics.

Table of Contents Previous Section Next Section Mainframe Screens, Convert to HTML

The first question to answer is, "When should the screens be converted?" The mainframe screens could be converted at execution timecompile time. Doing the mainframe screen conversions at execution time requires the scanning of the 3270 byte stream. Some changes may be needed to the source code to properly handle the conversion and processing of "control key" functions such as the clear, enter, PA-keys and PF-keys. This approach may offer a solution for simple applications that will be deployed within an enterprise via an Intranet. This approach by itself will not provide a solution for the more complex applications. This approach has been tried before to simply provide a GUI interface to an existing mainframe application and had limited success. The end result of this approach is to add another layer of complexity to an already complex production environment without positioning the application for the future in an expanding Internet environment.

Doing the mainframe screen conversions at compile time requires the conversion of the original BMS or MFS source members to HTML members. This approach will probably require some changes to the presentation logic prior to delivering business function directly to the customers of a company via the World Wide Web. The real value to this approach is realized when it is used as the first step in WEBerizing a legacy application by creating HTML components. This also positions the application for the future in an expanding Internet environment. When the appropriate development tools are used the screen conversions can be done quickly and will help the mainframe and Internet programmers begin to understand and leverage the best of both environments. Mainframe Express, a mainframe development tool provided by Micro Focus, has the ability to view, update or create BMS maps with its screen painter. This capability, combined with the BMS to HTML software, provides the mainframe programmer with an automated tool for converting BMS screens to HTML forms.

The mainframe screens to HTML forms conversion software should provide the following.

1. Support for the standard 24x80 character screens maintaining the original field locations on the screen.
2. Support for the 3270, model 5 screens maintaining the original field locations on the screen.
3. Support for multiple maps within a mapset.
4. Support for remapping function keys to submit buttons.
5. Support for JAVA Scripting to do functions such as cursor positioning.
6. Support for externally defining the foreground and background colors.
7. Support for externally defining font types and size.
8. Support for externally defining header and footer information for a screen. This is useful for adding a company logo or other information to the top or bottom of a screen.
9. Support for embedded 370 assembler statements.
10. Support for filtering HTML tags from mainframe screen text.

An additional benefit to the mainframe screen conversion is the ability to quickly model the application as it would appear in the Internet word. This model, when shared with the business users, could provide valuable feedback early in the conversion process.

Table of Contents Previous Section Next Section Combine & Change Screens, Application Code Changes

After the initial conversion of the mainframe screens to HTML forms the WEBerization process takes on a life of its own. Individual screens are improved in appearance and some screen sets are consolidated into a single HTML form and the subsequent paging logic removed from the application program.

For example, it is quite common to find data mapped across 2 or more screens because it would not fit on a single 24x80 character screen. The application programmers typically added the necessary presentation logic to use PF7 and PF8 to scroll forward and backward among the screens. The multiple screens can now be done within a single HTML form and the scrolling from the top to the bottom of the form can be done by the browser, thus simplifying the presentation logic by removing the code for handling PF7 and PF8.

Table of Contents Previous Section Next Section New Presentation Logic & Access to Application Server Data

New presentation logic will be needed as access to systems is provided outside a company. Providing access to business functions by individuals outside the company may require a much higher level of usability than many legacy systems provide. It should not be assumed that what can be accomplished within a company by a skilled employee can be easily mastered by a first time user that is not familiar with the application. Improved documentation or help text will be needed when an individual does not follow the business rules. Readily available help text will be a requirement when moving to the Internet.

Getting a text-based mainframe screen to look like a web page or form is only the first step. Getting the mainframe application to behave like a web application will require most of the work and require changes to the application code.

For larger networks or as network usage increases it may be advantageous to shift data from the mainframe to application server machines. Data base size, volatility and the requirement for immediate shared use by others will be three key factors that determine whether the master copy of a data set will reside on the mainframe or an application server. Many configurations will use a combination of the mainframe and the application servers. In some instances data will even reside on the client machines.

Table of Contents Previous Section Next Section Segment the Application & Distribute the Business Logic

Returning to the mainframe for every client request may not be the most efficient way to deliver information to individuals using the Internet. Identifying segments of business logic and creating components from these segments would allow business logic to be distributed to the application server machines. This should not be viewed as simply porting the code to the application server machine. The mainframe does an excellent job of processing multiple request from multiple users and keeps the individual requests and allocated resources in synchronization with the correct user and does all this concurrently with other processing. Providing this same capability at an acceptable performance level is a minimum requirement for an application server.

An application analysis tool such as Micro Focus Enterprise Analyzer could be used to reduce the analysis time and provide a better understanding of the application. Since most of the business logic on the mainframe is COBOL, an Internet-enabling tool for COBOL could be used to build distributed components.

Explore The Micro Focus Web Site for more information about products and services available from Micro Focus. This link requires an Internet Connection.

Applications running on a mainframe are usually written in COBOL. However, some applications are not written in COBOL and many applications are dependent on non-COBOL processes such as calls to 370 assembler subroutines, embedded calls to external sort routines and dependencies on batch processes to create and update existing data bases. Additional time should be allocated to handle these situations.

Table of Contents Previous Section Next Section Additional Topics

The need to quickly provide answers to complex questions for a growing audience is driving the transformation of mainframe applications to the Internet.

The technical challenge is to transform a centralized, predefined process based on terminal sessions to a distributed, event driven, sharing of processes based on application-to-application sessions. This is no longer an environment where a mainframe is polling and controlling a network of fixed-function terminals. This is a networked environment of machines communicating with machines on a peer to peer basis with the primary purpose of delivering information to people.

Table of Contents Previous Section Next Section Centralized or Distributed

Let's take a closer look at this transformation process starting with the Centralized to Distributed effort. In the centralized environment all the data, programs and business logic are performed on the host machine, in this case the mainframe . The first question to answer, "Is it necessary to transform from a centralized to a distributed approach?"

The answer, "It is going to be a compromise. Initially, some success could be obtained by simply converting from the 3270 technology to HTML technology." At this point we are describing a technology swap, not the segmenting and separating of the presentation logic from the business logic and data access logic.

As the transformation process continues the first thing to be distributed will be segments of the data. Shortly thereafter, selected programs and/or program segments will be distributed in order to meet the demands of the business requirements of a company.

One definition for distributed computing is, "Put the necessary computing power in the same location as the mission critical business requirements while making shared processes and data easily available across the enterprise with the proper controls for security and data integrity."

Table of Contents Previous Section Next Section Pre-defined or Event-Driven Processes

Many of the mainframe applications that need to be WEBerized are CICS or IMS. The initial objective was to structure the programs within these applications in such a manner that the presentation logic, business logic and data access logic were separate entities. In reality, the business logic and presentation logic became very interspersed.

The programs were designed and written to follow a predefined set of logic (i.e. sequence of events or code flow with some exception handling for data access errors. This predefined set of program logic was determined by the business rules and the requirements of CICS or IMS. The business logic and the presentation logic are so interspersed in many of today's applications that it is highly unlikely a generic solution that is capable of separating the two will be found in the time frame required to extend the application to the Internet.

There are tools available to help with the analysis of the applications but the segmentation (or componentization) of programs or parts of a program and the subsequent integration of these segments distributed across different machines will be done by the application developers.

Table of Contents Previous Section Next Section Transform, Terminal to Logic Based Sessions

As the presentation logic transforms from 3270 format to HTML forms the purpose of the application program changes from a terminal request to an application request that is data or process oriented. This transformation requires some additional analysis. For example, in a CICS application it is possible to get the terminal ID. Since the terminal ID is unique for each user this value is quite often used when obtaining temporary storage. If this technique is used then it would need to be removed or another technique would need to be implemented.

Table of Contents Previous Section Next Section The EBCDIC and ASCII Environments

Consideration must be given to the properties of the information being passed between the machines in a network. The mainframe works with EBCDIC information. The PC's and many Application Server machines work with ASCII information. When exchanging information between the mainframe and the application server or client machines the following items need to be considered.

1. Text fields are simply converted between EBCDIC and ASCII depending on the direction of information flow.
2. Text fields are simply converted between EBCDIC and ASCII depending on the direction of information flow.
3. Binary fields may need to be inversed.
4. Floating point values.
5. Sorting results in different sequencing for EBCDIC and ASCII files containing the same information.
6. Unique requirements of the programming language being used on the application server or client machines.
7. If crossing international boundaries then different code pages will be needed for the conversion.

Table of Contents Previous Section Next Section JAVA Script to Complement HTML

HTML alone will not provide the necessary function to get to an acceptable conversion from mainframe screens to usable HTML forms. The use of JAVA Scripting will be needed to fine-tune the HTML. For example, the positioning of the cursor in a field on a 3270 screen must be converted to placing focus on the field within the HTML form. Another example would be the validation of digits within a numeric field.

Table of Contents Previous Section Next Section The Mainframe Connection

Many companies want to include the mainframe as a major player functioning in its traditional roll and taking on the new roll of a very powerful server and large data base manager. The mainframe connection may be divided into two sections. One, how to connect the client (or application server) to the mainframe and two, what to do once the connection is established. The "how to connect to the mainframe" has expanded beyond the SNA environment and now includes the TCP/IP environment. Today, most mainframes have TCP/IP networks installed and the remaining few have plans in place to add TCP/IP capability based on business requirements. For the client/server environment or the PC-to-mainframe environment TCP/IP has become the primary connectivity option. The "what to do once the connection is established" are the requirements that need to be defined. These requirements are what differentiate connectivity software from middleware. These requirements will be different across companies but there are some similarities.

1. Access to data or sharing of data
2. Access to process or sharing of process
3. Immediate processing
4. Deferred processing or shifting of processing

Let's take a closer look at each of the above items.

Table of Contents Previous Section Next Section Access to Data or Sharing of Data

This requirement could be as simple as retrieving a single record from a data base and passing the information back to the client. However, this level of simplicity is usually the exception. The mainframe data is usually stored in EBCDIC format and may contain packed, binary or floating point data. These data formats would need to be emulated or converted for use on a PC client. In addition, the information being requested by a client may require access to multiple records within a data base or access to multiple data bases of varying type and structure. In some instances it may be desirable to download a data base or a subset of a data base to the application server or client machine.

Table of Contents Previous Section Next Section Access to Process or Sharing of Process

The client needs to be able to submit a request for processing that may include additional data that is sent (uploaded) to a server machine. The server machine, in this case the mainframe, needs to be able to perform the processing of the collected information and return the results of the processing cycle to the client. In some instances it may be desirable to download the processing components to an application server or client machine.

Table of Contents Previous Section Next Section Immediate Processing

When a client makes a request that requires processing (i.e. the running of an application program) and expects an answer in less than a second (or at least within seconds or minutes) then a networked systems must be able to do the processing immediately and concurrently with other system processes being performed at the time of the request.

Table of Contents Previous Section Next Section Deferred Processing or Shifting of Processing

Sometimes a client request or part of a request may not require immediate processing. For example, a client may submit an order for merchandise and would expect the stock to be allocated immediately, the shipping to occur within 24 hours and the billing to take place within the next thirty days. The billing event needs to be posted but the actual billing process may be deferred.

Many times competitive pressures cause a shifting in processing requirements. For example, the Internet has changed the way many insurance companies respond to requests for policy quotes. It was acceptable for an insurance agent to submit a request for a policy quote that included information about an individual requesting the quote. In the past the insurance agent would submit the request and additional information. The request would be scheduled to run overnight on a regularly schedule run that processed all the requests received during the day. The insurance agent would sign-on to the system the following day and if all the information was submitted correctly they would received their policy quote. Otherwise, they would receive a message describing the reasons why the request was not processed. In today's environment insurance agents expect to be able to get a policy quote in less than five minutes. Also, as companies expand to global markets and the use of the Internet increases the availability of the mainframe's night time window of low utilization that has been used for batch processing is shrinking. It is rapidly becoming a twenty-four hour day with immediate processing requirements.

Table of Contents Previous Section Next Section Questions

Many companies will answer "Yes" to at least four of the following questions with some larger companies answering "Yes" to six or seven.

1. Do you need to create and deploy new applications that deliver new business function via the Internet?
2. Do you need to extend existing mainframe applications and use the Internet as the delivery vehicle for your existing business functions?
3. Do you need help in converting existing CICS, BMS screens to HTML documents?
4. Do you need help in converting existing IMS, MFS screens to HTML documents?
5. Do you need help in converting existing CICS, BMS screens to HTML documents?
6. Do you need access and sharing of mainframe resources and distributed systems via TCP/IP networks?
7. Do you need a better way to connect your browsers to servers to mainframes that allow applications or parts of applications to reside on different systems and share information and processes?

The preceding questions and the answers provided from within a company need to be addressed prior to starting a Legacy to Internet project. Many companies will need to complement the skills and bandwidth of internal resources with contracted consulting, additional training and possible programming services.

Table of Contents Previous Section Next Section Summary

The intent of this document is to provide readers with various alternatives and possible issues when extending mainframe legacy applications to the Internet. This document may be used as a tutorial for new programmers or as a quick reference for experienced programmers.

In the world of programming there are many ways to solve a problem. This document and the links to other documents are intended to provide a greater awareness of the Data Management and Application Processing alternatives.

The documentation and software were developed and tested on systems that are configured for a SIMOTIME environment based on the hardware, operating systems, user requirements and security requirements. Therefore, adjustments may be needed to execute the jobs and programs when transferred to a system of a different architecture or configuration.

SIMOTIME Services has experience in moving or sharing data or application processing across a variety of systems. For additional information about SIMOTIME Services or Technologies please send an e-mail to: helpdesk@simotime.com or call 415 883-6565. We appreciate hearing from you.

Table of Contents Previous Section Next Section Software Agreement and Disclaimer

Permission to use, copy, modify and distribute this software, documentation or training material for any purpose requires a fee to be paid to SimoTime Technologies. Once the fee is received by SimoTime the latest version of the software, documentation or training material will be delivered and a license will be granted for use within an enterprise, provided the SimoTime copyright notice appear on all copies of the software. The SimoTime name or Logo may not be used in any advertising or publicity pertaining to the use of the software without the written permission of SimoTime Technologies.

SimoTime Technologies makes no warranty or representations about the suitability of the software, documentation or learning material for any purpose. It is provided "AS IS" without any expressed or implied warranty, including the implied warranties of merchantability, fitness for a particular purpose and non-infringement. SimoTime Technologies shall not be liable for any direct, indirect, special or consequential damages resulting from the loss of use, data or projects, whether in an action of contract or tort, arising out of or in connection with the use or performance of this software, documentation or training material.

Table of Contents Previous Section Next Section Downloads and Links

This section includes links to documents with additional information that are beyond the scope and purpose of this document. The first group of documents may be available from a local system or via an internet connection, the second group of documents will require an internet connection.

Note: A SimoTime License is required for the items to be made available on a local system or server.

Table of Contents Previous Section Next Section Current Server or Internet Access

The following links may be to the current server or to the Internet.

Note: The latest versions of the SimoTime Documents and Program Suites are available on the Internet and may be accessed using the Link to Internet icon. If a user has a SimoTime Enterprise License the Documents and Program Suites may be available on a local server and accessed using the Link to Server icon.

Link to Internet   Link to Server   Explore the Java and COBOL document that presents the results of a project that converted a CICS, COBOL and BMS transaction to a Java, COBOL and JSP transaction.

Link to Internet   Link to Server   Explore An Enterprise System Model that describes and demonstrates how Applications that were running on a Mainframe System and non-relational data that was located on the Mainframe System were copied and deployed in a Microsoft Windows environment with Micro Focus Enterprise Server.

Link to Internet   Link to Server   Explore the COBOL Connection for more examples of COBOL programming techniques and sample code.

Link to Internet   Link to Server   Explore The ASCII and EBCDIC Translation Tables. These tables are provided for individuals that need to better understand the bit structures and differences of the encoding formats.

Link to Internet   Link to Server   Explore The File Status Return Codes to interpret the results of accessing VSAM data sets and/or QSAM files.

Table of Contents Previous Section Next Section Internet Access Required

The following links will require an internet connection.

A good place to start is The SimoTime Home Page for access to white papers, program examples and product information. This link requires an Internet Connection

Explore The Micro Focus Web Site for more information about products and services available from Micro Focus. This link requires an Internet Connection.

Table of Contents Previous Section Next Section Glossary of Terms

Link to Internet   Link to Server   Explore the Glossary of Terms for a list of terms and definitions used in this suite of documents and white papers.

Table of Contents Previous Section Next Section Comments or Feedback

This document was created and is copyrighted and maintained by SimoTime Technologies.

If you have any questions, suggestions, comments or feedback please call or send an e-mail to: helpdesk@simotime.com

We appreciate hearing from you.

Table of Contents Previous Section Next Section Company Overview

SimoTime Technologies was founded in 1987 and is a privately owned company. We specialize in the creation and deployment of business applications using new or existing technologies and services. We have a team of individuals that understand the broad range of technologies being used in today's environments. Our customers include small businesses using Internet technologies to corporations using very large mainframe systems.

Quite often, to reach larger markets or provide a higher level of service to existing customers it requires the newer Internet technologies to work in a complementary manner with existing corporate mainframe systems. We specialize in preparing applications and the associated data that are currently residing on a single platform to be distributed across a variety of platforms.

Preparing the application programs will require the transfer of source members that will be compiled and deployed on the target platform. The data will need to be transferred between the systems and may need to be converted and validated at various stages within the process. SimoTime has the technology, services and experience to assist in the application and data management tasks involved with doing business in a multi-system environment.

Whether you want to use the Internet to expand into new market segments or as a delivery vehicle for existing business functions simply give us a call or check the web site at http://www.simotime.com


Return-to-Top
Legacy Systems, Mainframes and the Internet
Copyright © 1987-2019
SimoTime Technologies and Services
All Rights Reserved
When technology complements business
http://www.simotime.com