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Accessing CICS Applications with Alternate Screen Sizes via HostBridge

From Russ
December 5, 2008

Friends,

Here’s an issue recently raised by one of our customers. I put together an answer for them and then thought it might be of value to others as well.

Some CICS applications have been designed to exploit alternate screen sizes of IBM 3270 terminals. For example, a CICS application that displays printed reports might be capable of driving a 3270 Model 5 terminal in its 132 column mode. HostBridge does support CICS applications that exploit a terminal’s alternate screen size. So how do you enable this?

Whenever HostBridge creates a bridge facility/session within CICS, it does so based on the characteristics of a specific type of terminal. By default, HostBridge/CICS reference a TERMINAL definition named CBRF to acquire general characteristics:

CEDA  View TErminal( CBRF )                                                 

 TErminal       : CBRF                                                      

 Group          : DFHTERM                                                   

 Description    : Default 3270 Bridge template                              

 AUTINSTModel   : No                 No | Yes | Only                        

 AUTINSTName    :                                                            

TERMINAL IDENTIFIERS                                                        

 TYpeterm       : DFHLU2                                                    

 NEtname        : CBRF                                                       

 CONSOle        : No                 No | 0-127 | 129-250                   

 CONSName       :                                                           

 REMOTESYSTem   : CBR                                                        

 REMOTEName     : CBRF                                                      

 REMOTESYSNet   :                                                           

 Modename       :                                                           

 ...


Note that CBRF references a TYPETERM definition named DFHLU2 to obtain more specific device characteristics. The TYPETERM definition indicates the terminal model, as well as the primary and alternate screen size (actually, in two places):

CEDA  View TYpeterm( DFHLU2   )                                             

 TYpeterm       : DFHLU2                                                    

 Group          : DFHTYPE                                                   

 DEScription    :                                                            

RESOURCE TYPE                                                               

 DEVice         : LUTYPE2                                                   

 TERmmodel      : 2                                                          

 SESsiontype    :                                                           

 LDclist        :                                                           

 SHippable      : Yes                No | Yes                               

MAPPING PROPERTIES                                                          

 PAGesize       : 024 , 080          0-255

 ALTPage        : 000 , 000          0-255                                  

 ALTSUffix      :                                                            

 FMhparm        : No                 No | Yes                               

 OBOperid       : No                 No | Yes                               

PAGING PROPERTIES                                                            

 AUTOPage       : No                 No | Yes                               

DEVICE PROPERTIES                                                           

 DEFscreen      : 024 , 080          0-255

 ALTSCreen      :     ,              0-255                                  

 ...

APPLICATION FEATURES                                                        

 BUildchain     : Yes                No | Yes                               

 USerarealen    : 000                0-255                                  

 Ioarealen      : 00256 , 04000      0-32767                                

 UCtran         : Yes                No | Yes | Tranid                      

 ...


DFHLU2 specifies a primary screen size of 24x80, but no alternate screen size. Furthermore, CBRF and DFHLU2 are IBM-provided definitions and can’t be modified. Thus, to cause HostBridge and the target CICS application to use an alternate screen size, you must define/use alternate TERMINAL and TERMTYPE resources.

As part of the HostBridge installation, alternate TERMINAL and TERMTYPE definitions are installed: HBRF and HBRLU2. These definitions are identical to CBRF/DFHLU2 except that:

•    HBRF references TYPETERM HBRLU2

•    HBRLU2 defines the USERAREALEN parameter as 255 bytes (this parameter defines the length of the TCTUA and is the most common reason why customers use these alternate definitions).

As provided, TYPETERM HBRLU2 does not define an alternate screen size. Thus, the first step is to change the definition of HBRLU2 such that an alternate screen size is specified. Alternatively, you could copy HBRLU2 and create a new TYPETERM definition (as well as a new TERMINAL definition which references it). For example:

 

CEDA  View TYpeterm( HBRLU2   )                                             

 TYpeterm       : HBRLU2                                                    

 Group          : DFHTYPE                                                   

 DEScription    :                                                            

RESOURCE TYPE                                                               

 DEVice         : LUTYPE2                                                   

 TERmmodel      : 5                                                          

 SESsiontype    :                                                           

 LDclist        :                                                           

 SHippable      : Yes                No | Yes                               

MAPPING PROPERTIES                                                          

 PAGesize       : 024 , 080          0-255

 ALTPage        : 027 , 132          0-255                                  

 ALTSUffix      :                                                            

 FMhparm        : No                 No | Yes                               

 OBOperid       : No                 No | Yes                               

PAGING PROPERTIES                                                            

 AUTOPage       : No                 No | Yes                               

DEVICE PROPERTIES                                                           

 DEFscreen      : 024 , 080          0-255

 ALTSCreen      : 027 , 132          0-255                                  

 ...

APPLICATION FEATURES                                                        

 BUildchain     : Yes                No | Yes                               

 USerarealen    : 255                0-255                                  

 Ioarealen      : 00256 , 04000      0-32767                                

 UCtran         : Yes                No | Yes | Tranid                      

 ...

               

Assuming you changed TYPETERM HBRLU2, and that TERMINAL HBRF references HBRLU2, then all you need to do is tell HostBridge to create the bridge facility based on TERMINAL HBRF. To do this, you specify the directive hb_facility_like=HBRF with the HostBridge request (hb_terminal is a synonym for hb_facility_like).

HostBridge directives can be specified in a number of different ways. Since hb_facility_like controls fundamental attributes of the bridge facility, it can be specified two ways:

•    On the first request sent to HostBridge to create the session (via an individual HTTP request or via a HostBridge script);

•             In the HBR@SESS command file (which is processed with the first request of the session).

Provided these steps are followed, a CICS application that supports should adapt accordingly and send output in that mode.  HostBridge will also adapt accordingly and include the contents of the entire page/screen in the XML response (or make the entire page/screen available within the script).

* * *
There you have it.

More later.

Russ