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FAQs: Existing CICS Applications

The list is by no means exhaustive, so please feel free to mail us questions about any topics we fail to cover here.

Here are some of the topics covered in our FAQ.

Can I access the same application using both HostBridge and 3270 terminals (real or emulated)?

Absolutely. Remember that HostBridge requires no changes to your existing CICS applications: no changes, no recompiling, nothing. As a result, CICS applications can be used from real 3270 terminals, PC’s with emulators, and HostBridge simultaneously. The application will never know the difference. While we would like to take credit for this feat we really can’t. This is just how the CICS 3270 Bridge feature works. If you care to know why, read on…

A transaction is started under CICS when a program issues a START request specifying the name of the transaction. When you access CICS from a 3270 terminal (real or emulated), your session is being managed by special program within CICS (we will refer to it as the “terminal handler”). It is the terminal handler that interacts with you at the terminal and allows you to specify the name of the transaction in the upper left corner of the screen. The terminal handler receives the information from the terminal and issues the START request to invoke the transaction.

When using HostBridge, the process is similar except that the CICS terminal handler program is not used. Instead, HostBridge receives a request to execute a transaction via HTTP (or possibly ECI). Upon receiving a request, HostBridge issues the START command to invoke the specified transaction.

When IBM added the 3270 Bridge feature to CICS, they added a new parameter to the START command. This command allows the issuer to specify the name of a “bridge exit” that is to receive control whenever the transaction issues a BMS or terminal control operation (e.g., SEND MAP). This process of CICS passing control to a bridge exit (i.e., HostBridge) is totally transparent to the CICS application.

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Can HostBridge be used to automate access to a sequence of CICS transactions?

Yes, and without forcing customers to use proprietary scripting languages. A more detailed answer follows.

While HostBridge changes the way a CICS BMS transaction communicates (XML instead of 3270), it does not change the way a CICS application is organized internally (that would require changing the application). Stated differently, HostBridge changes the way a CICS application “speaks”, but not the way it “thinks”

Various factors guide a CICS application developer in how transactions are organized (e.g., workflow, processing efficiency, display screen capacity and ease of programming). Transactions are usually designed to be either “conversational” or “pseudo-conversational”. Once started, a conversational transaction interacts with the end user multiple times before it terminates. Because they can run for an extended period of time, conversational transactions are usually discouraged for reasons of processing efficiency. Pseudo-conversational transactions appear to the end user to behave like a conversational transaction. However, the application has been designed such that each interaction with the user is a separate transaction.

Regardless of which technique is used, applications are frequently designed such that multiple interactions/transactions are required to complete a specific work process. And, if this is true without HostBridge, it is also true with HostBridge: multiple interactions between HostBridge and the CICS application (via HostBridge) are still required. It is this situation that raises the question as to how HostBridge can be used to automate, or “script”, these multiple interactions.

If a customer wants to perform transaction/process automation on the host, we suggest that they use the standard scripting languages and process automation tools such as those supported by HostBridge Extended.

However, if a customer wants to perform process automation from the middle-tier, they are free to use whatever application development environment they already use (provided it supports HTTP and XML). Alternatively, customers could use a product that specializes in XML-based process automation, such as eXtend from Novell Software. (Please refer to the FAQ question “Can HostBridge be used with Novell eXtend?”)

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