CICS User Guide
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To understand how the BEA Tuxedo Mainframe Adapter for TCP (CICS) (hereafter referenced as TMA TCP for CICS) product works, you should know how the product performs the following functions:
Each of these operations is described in the following sections. Additionally, this document describes some programming considerations that may be useful when you develop or change programs that interoperate with TMA TCP for CICS.
The Listener program is supplied by IBM and is part of the Sockets for CICS software product which must be purchased from IBM.
Note: Before you can use TMA TCP for CICS, you must install and configure both IBM TCP/IP and the Sockets for CICS product as outlined in the documentation that accompanies those products.
The Listener's job is to wait for connection requests at a particular network address and port of your choosing. When the Listener receives a connection request it invokes the appropriate CICS program automatically, based on the name supplied as part of the Listener's connection protocol buffer. For example, if the Listener receives a connection request from TMA TCP gateway running on a remote BEA Tuxedo node, it processes the connection and invokes the TMA TCP Handler.
The TMA TCP Handler is invoked automatically by the Listener process. Once invoked, the Handler takes control of the socket connection and retains control until either the Handler is shut down or until there is a network problem that affects the socket connection. The Handler processes service requests up to the configured multiplex count. To process more service requests than the configured multiplex count, TMA TCP gateway starts more than one Handler. For limitations of the IBM Sockets for CICS Listener, refer to the appropriate IBM product documentation.
The very first service request that is sent from the TMA TCP gateway gateway running on a remote BEA Tuxedo node causes the following to occur.
LINK
command to execute the program specified in the TMA TCP protocol header. With the LINK
command it also passes along any request data provided by the client application that made the original BEA Tuxedo service request.EXEC CICS START TRANS
call with the transaction specified in the Inbound Service File for the service specified in the TMA TCP protocol header. The transaction should be the same as the Application Handler program.Note: If security is enabled, the EXEC CICS START TRANSID
call uses the user ID
specified in the TMA TCP protocol header.
For tpacall/TPNOREPLY
requests, the remote program is invoked by a CICS
START TRANSID
command and no data is returned to the original caller. In this case, a unique transaction must be defined for the service. Use the Inbound Service Information screen to enter this unique transaction name rather than using the transaction name that starts the Application Handler.
When the network connection is lost, the Handler process automatically shuts down. The next service request sent causes the Listener to automatically start a new Handler, if necessary.
Use the supplied shutdown transaction BDWN
to terminate active TMA TCP for CICS programs. Depending on the options specified, this causes all Handlers to shut down gracefully. The name of the BDWN
transaction may have been changed at your site during installation, so verify the name.
You can use the BDWN
transaction in a CICS region with the following parameters to shut down Handlers in various ways. The command line syntax for BDWN
is illustrated in the following listing.
Listing 2-1 BDWN
Command Line Syntax for Handlers
BDWN [ALL | CLEANUP | HANDLER I | HANDLER]
Shuts down all Handlers or all Requesters or both. It also frees shared memory that was allocated by a Handler that has abended without freeing the shared memory that it allocated. You can specify optional parameters with the BDWN
transaction to shut down Handlers immediately or after the processing of all requests has completed. The default is ALL
.
The Requester is started automatically when the first service request for it is made by a CICS client program. At that point, the Requester establishes a connection with its remote endpoint and updates its control tables with run-time information for use by subsequent requests. If the connection with the remote endpoint is lost for any reason, the Requester attempts to re-establish the connection automatically. After a configured number of unsuccessful connection attempts, the Requester marks itself disabled.
If the gateway receives additional service requests, they are accommodated as long as the maximum multiplex count for the existing connection is not exceeded. Also, additional connections are opened, as necessary, until the configured maximum connection count is reached or all requests are accommodated.
EXEC CICS LINK
command to the TMA TCP for CICS Pre-requester. There are two ways to shut down the Requester:
BDWN
. This method causes ALL Requesters to shut down gracefully. The name of the BDWN
transaction may have been changed at your site during installation. Check with the person who installed TMA TCP for CICS at your site. You can use the BDWN
transaction in a CICS region with the following parameters to shut down Requesters in various ways. The command line syntax for BDWN
is illustrated in the following listing.
Listing 2-2 BDWN
Command Line Syntax for Requesters
BDWN [ALL | REQUESTER I | REQUESTER]
Shuts down all Handlers or all Requesters or both. It also frees shared memory used by the Requesters associated with each logical machine ID (LMID
). You can specify optional parameters with the BDWN
transaction to shut down Handlers or Requesters immediately or after processing of all requests has completed. The default is ALL
.
Due to the way TMA TCP gateway translates and converts data on the remote BEA Tuxedo system, the CICS programmer does not need to do anything to prepare data that is destined for the remote BEA Tuxedo system.
The key to this high degree of transparency is the TMA TCP gateway configuration. It is through this mechanism that environmental differences, such as naming conventions and data formats, are concealed from programmers and programs.
Although all data is converted and translated automatically by the remote TMA TCP gateway gateway, the rules implemented are outlined in the following subsections to assist the CICS programmer in understanding how the data is manipulated. It is important for the CICS programmer to remember that this information is written from the point of view of the BEA Tuxedo environment.
When a client program on the remote BEA Tuxedo system sends data to (or receives data from) a service routine on a different model of computer, TMA TCP gateway automatically translates data as required. Translation involves changing the representation of intrinsic data types by changing attributes such as word length and byte order.
The following subsections describe the basic rules that TMA TCP gateway follows when it translates data and provide detailed information about how TMA TCP gateway handles string and numeric data.
The following terms are some commonly used BEA Tuxedo terms for buffer types.
The following table lists the data translation rules that TMA TCP gateway follows.
Note: BEA Tuxedo provides a field type named dec_t that supports decimal values within VIEW
s. The TMA TCP gateway product translates these fields into machine independent representations of packed decimals. For example, dec_t(m,n)
becomes S9(2*m-(n+1))V9(n) COMP-3
. Therefore, a decimal field with a size of 8,5 corresponds to S9(10)V9(5) COMP-3
.
The following table summarizes the translation rules between C and IBM/370 data types.
This subsection provides suggestions that help you develop VIEW
definitions for input and output buffers and records. It also explains how string data and numeric data are treated in the TMA TCP gateway environment.
When you create VIEW
definitions for input and output records that are used by CICS applications, do not specify an extra position for the terminating NULL characters that are used in string fields.
For example, when a CICS application program expects 10 characters in an input record, specify 10 for that field, not 10 plus 1.
Note: Although TMA TCP gateway does not require strings to be NULL-terminated, it respects NULL termination. Therefore, when TMA TCP gateway detects a NULL (zero) character within a string, it does not process any subsequent characters. To pass full 8-bit data that contains embedded NULL values, use a CARRAY
type field or buffer.
The character set translations performed by TMA TCP gateway can be fully localized, in accordance with the X/Open XPG Portability Guides. ASCII and EBCDIC translations are loadable from message files. The TMA TCP gateway software contains default behaviors which should meet the requirements of most English-language applications. However, you may find it necessary to customize tables. See the BEA TMA TCP gateway User Guide for complete instructions.
You can convert numeric data into different data types easily, provided that you have enough range in the intermediate and destination types to handle the maximum value you need to represent.
For example, you can convert an FML field of double into a packed decimal field on the remote target system by specifying an appropriate dec_t type VIEW
element.
In addition, you can convert numeric values into strings (and the reverse). For example, while FML buffers do not directly support the dec_t type
, you can place decimal values in string fields and map these to dec_t fields
within VIEW
definitions.
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