CICS/VS Data Communications Design 33

INPUT

... -D-e-v-ic-e.-d-e-pe-n-d·-e-n-t -CO-d-e-' -m-a-y-be-r-em-o-ve-d-··-by-p-ro-g-r-a:-x For the 3600 and 3650, input mapping requests are ignored. ...

:-e:-:-I.::'::t7::::~~:UC~::~-h;~360:

I

---,_._."--, ,----,

Figure 3-2. CICS/VS Terainal Device Independence

• 3780 comaunication Systea

• 360~ Finance Ccmmunicaticn SysteD (BMS input requests are ignored)

• 3650 Retail stcre System

Furthermore, the following seguential devices can be used to simulate online terminals, and transmit simulated terminal messages to and from the systelo:

34 CICS/VS System/Application Design Guide

• Card reader/line printer

• Tape drives

• Disk drives INPUT MESSAGES

ClCS/1S accepts input messages frem any of the above devices and, using the input map specified by the application program, converts the input message into a fixed fermat message, as specified ty that map.

Device-dependent characteristics in the input message are removed, and the appropriate fields are selected from the message and inserted in fixed locations in the mapped message.

In the case of the 3600, device-dependent characteristics in the input message are removed ty the 3601 Controller and the input message is formatted for CICS/VS applicatien program processing before

transmission to ClCS/VS. Consequently, BMS input mapping requests associated with 3600 input messages are ignored, and the data received from the 3600 is passed to the CICS/VS applicaticn program without change. See "Basic Mapping Suppcrt Using VTAM" for additional information.

OUTPUT MESSAGES

output messages fer transaissicn to terminals can be prepared without the control characters required for field positicning, or line

separation. output Dessages can be Fresented to CICS/VS as a data

stream. Optionally, the application program can insert new line (X'1S') characters in the output data stream if required.

CICS/1S device-independent sUFPcrt divides the data stream into lines no longer than those defined for the particular terminal. If new-line characters appear occasionally in the data stream to further define line lengths, they are honored. CICS/VS inserts the appropriate leading characters, carriage returns, and idle characters, and truncates trailing blanks from each line.

Terminal device independence permits an application program to be independent of the terminal type (or types) in the installation, and can provide for support of mixed terminal types ty the same program.

This allows the use of backup ter.inals of a different type, or

changeover of hard-copy terminals to display terminals when transaction volumes warrant the change, with little or no additional programming

eff~rt. It also reduces the amount cf program maintenance necessary when changes are made in the terminal devices used by online programs, and permits increased growth flexitility in the installation.

Terminal device independence is the only EMS support available with the subset option of CICS/DOS/VS. Terminal paging and message routing are not supported. (See "CICS/DOS/VS Subset Option" in Chapter 7.)

Terminal paging is an additional feature that extends the capatilities of terminal device indeFendence. The application programmer can prepare mere output than can be conveniently or physically displayed at the receiving terminal. That output can be presented by CICS/VS as a series of pages. CICS/VS identifies and saves each page of infor.aticn prepared by the application program.

Chapter 3. CICS/1S Data Communications Design 35

INPUT

Terminal paging further relieves the application programaer of the need to ccncern himself with the p~esentation of infor.ation in a form 36 CICS/VS systea/Application Design Guide

suitable for display at the appropriate terminal, or with presentation of that information to the terminal in the sequence requested by the terminal operator. The ap~licaticn ~rogram.er can nov prepare a series of pages of information, on the assumption that the terainaloperator may wish to examine all of that information, and then present those pages directly to CICS/VS. Ne further programming is necessary to handle the selection of ~ages for display at the terminal. Page selection is made by the terminal operator, using the CICS/VS paging commands.

This will simplify program development of conversational applications and consequently increase prcgra.mer productivity and decrease the

amount of future program maintenance necessary.

It is important that the system designer recognize that terminal pages are saved ty CICS/VS in temporary storage. Temporary storage may be supported in main storage alone, or on auxiliary storage using VSAM; both will increase the demands for real stcrage during execution.

Using VSAM on a CPU with limited real storage available for virtual storage paging may increase ^~aging and therefore influence online

performance. Refer to Chapter 1 for recommended ainimum CPU sizes when VSAM is used. Terminal ~aging is not supported by the subset option of CICS/tOS/VS. (See "CICS/DOS/VS Subset Option.")

TERMINAL PAGING STATUS

Terminal paging is particularly oriented toward display terminals.

However, it can also be used for hard-copy terminals. A terminal can be defined as having a "reguest ~aging" status or an "automatic paging"

status.

Display terminals must use a request paging status, while hard-copy terminals can use either request ~aging or automatic paging status.

Request paging status enables pages to be displayed at the terminal on request by the terminal operator, whe can specify the sequence of pages to be displayed based upon his requirements.

Automatic paging status, such as normally used for a hard-copy terminal, causes CICS/VS tc automatically output the next page of information on completion ef a previcus page. In this way, all information is presented tc the hard-copy terminal in a continuous

output stream. If required, an automatic paging terminal may be changed to request paging status by either the terminal operator or the

application program, enabling only those pages to be printed which are of significance to the terminal cperator. Similarly, the terminal operator or the application program can change request paging status to automatic paging for all terminals except display terminals.

Other terminal status specificaticns can also be used to indicate whether a terminal automatically receives messages sent from the CPU or from cther terminals. This is discussed under "Terminal Status" in Chapter 4. Additional infcrmaticn on terminal paging can be found in the ~lCSL!~ ABB!j~§!i2D fI2g1~!!§I!§ jef§I~~§ ~~~s!, SH20-9003.

Message routing directs messages to one or more terminals in the system, either by use of the message switching transaction, CMSG, supplied by CICS/VS, or by the E!S ROUTE macro instruction. In this context, the term "message switching" refers to the use of CMSG. The term "message routing" refers to the use of the EMS ROUTE macro

instruction. (The CMSG transaction itself uses the services of the EMS BOUTE macro instructicn.)

Chapter 3. CICS/VS Data Communications Design 31

The CMSG transaction is entered by a terminal operator together with a message to be directed tc ancthel= terminal, or to several terminals identifiecl by the terminal oFera tor.. (This is discussed further in

"Message switching Transactien (C!!SG)" later in this chapter.)

The message routing macro instruction permits an application program to send messages to one or mere terminals not in direct centrol of the transaction. Message routing uses EMS, and saves messages in temporary storage to be automatically sent to the specified destination terminals if the status of those tEruinals allcws for reception of the messages

(refer to "Terminal Status" in ChaptEr 4). If a terminal is not immediatEly eligible to receive the message, CICS/VS preserves it in tempoary storage until such time as a change in terminal status allo.s it to be sent, cr a user-sFecified period of timE elaFses, whichever occurs first (see Figure 3-4). The message to te delivered is separated into a message for each terminal type that will receive it. Each

separate terminal-type message is saved in tempoary storage, together with a destination terminal list fer that particular terminal type.

In addition, an applicaticn Frogram can prepare pages of information to be transmitted to terminals, using EMS and the terminal paging

facilities as described above. These Fages can te routed to one or more terminals or operators, through the use of the BMS ROOTE macro instruction.

MESSAGE DELIVERY

The application programmer spEcifies the identification of the terminal (or terminals) to receivE the message, and, optionally, can also specify a time when the message is to be delivered. If the message cannot be delivered either iaaediately or at the sFecified future time, CICS/VS retains the message fcr a user-specified period of time. If it still <:annot be dElivered, CICS/VS notifies the originating terminal or an alternative terminal sFecified when the original message was entered.

CICS/VS allows messagEs to be dirEcted, not only to specific

terminalsv but also to sFecific operators or operator classes. In this way, sensitive security information will only te delivered to those operators authorized to receive it. It is retained in temporary storage until the specified operaters sign on to the specified terminals, and only then will relevant messages te dElivered.

If a message is to be sEnt to a specified operator without

identifying a terminal, that operator must already be signed on when the message is first presented te CICS/VS to establish the terminal identificatien tc be used. If a message is sent to a specific operator and terminal, and that operator can never use that terminal (because of geographic location, for exam FIe), the message will be accepted by CICS/VS but may never be dEliverEd. This is noted by CICS/VS upon expiratien of thE specified time within which the message must be delivered ..

Terminals in the IBM 3600 PinancE Communicatien System are identified

by a lcgical device code (tDC). Me_sages from CICS/VS are received by the appropriate 3601 application program which represents the specified terminal ID and controls the devices attached to the 3601. The message from CIeS/VS identifies the IDC (SFecified by the application

programmer) that is to rEceive the messagE; it is the responsibility of the 3601 application Fregram to ensure that the message is delivered to the device indicated ty the LDC. Logical device codes are described in detail in "Basic !apping Suppert Osing VTAM" in this chapter.

38 CICS/VS System/Application Design Guide

INPUT