Using data conversion with Link3270

If the codepage of your client program is different from the codepage used by the CICS® user program, your messages need to be converted.

The BRIH, all BRIV vector headers and RETRIEVE data can be converted using the CICS conversion program DFHCCNV. See the CICS Family: Communicating from CICS on System/390® manual for information about the data conversion process.

DFHCCNV uses the DFHCNV table to determine the required conversions. You need to supply entries in this table for each resource that requires conversion. See the CICS Family: Communicating from CICS on System/390 manual .

Converting BRIH and BRIV header data

In your DFHCNV, you should include:

COPY DFHBRCTD

If you are using codepages other than the defaults, that is, other than 437 for the client and 037 for the server, then you must ensure that the correct codepage conversion is applied to DFHBRCTD. You can do this by coding SRVERCP and CLINTCP parameters on the DFHCNV TYPE=INITIAL statement. The COPY DFHBRCTD statement should follow DFHCNV TYPE=INITIAL.

If the application programs run using the same codepages as those specified on the TYPE=INITIAL statement, then the TYPE=ENTRY statements do not need to specify the codepages.

If an application program, or programs, need to use different codepages, then the new values must be specified on the appropriate TYPE=ENTRY statements.

Build DFHCNV as described in the CICS Family: Communicating from CICS on System/390 manual . This will convert the BRIH and BRIV vector headers using the codepages described in your conversion template.

DFHCNV example for Link3270

Figure 11 shows an example of a DFHCNV for a CICS region using codepage 939 for the server programs and codepage 943 for most of the clients.

The COPY DFHBRCTD statement follows the DFHCNV TYPE=INITIAL statement, so it will use 939 and 943. This is used in the conversion of BRIHs.

PROG1 uses the same codepages, but PROG2 uses client codepage 932 instead of 939. In order to achieve this, the TYPE=ENTRY statement for PROG2 contains overrides for the client and server codepages.

Figure 11. DFHCNV example for Link3270
DFHCNV   TITLE 'EXAMPLE DFHCNV CONVERSION TABLE'               
*                                                                              
         DFHCNV TYPE=INITIAL,SRVERCP=939,CLINTCP=943                           
*                                                                              
         COPY DFHBRCTD                                                         
*                                                                              
         DFHCNV TYPE=ENTRY,RTYPE=PC,RNAME=PROG1                                
         DFHCNV TYPE=SELECT,OPTION=DEFAULT                                     
         DFHCNV TYPE=FIELD,OFFSET=0,DATATYP=CHARACTER,DATALEN=10018,   *       
               LAST=YES                                                        
*                                                                              
         DFHCNV TYPE=ENTRY,RTYPE=PC,RNAME=PROG2,                       *       
               SRVERCP=939,CLINTCP=932                                         
         DFHCNV TYPE=SELECT,OPTION=DEFAULT                                     
         DFHCNV TYPE=FIELD,OFFSET=0,DATATYP=CHARACTER,DATALEN=500,     *       
               LAST=YES                                                        
*                                                                              
         DFHCNV TYPE=FINAL                                                     
         END                                      

Converting RETRIEVE data

RETRIEVE data is converted using the conversion template for the user transaction. You should provide a DFHCNV entry with RTYPE=IC RNAME=user tranid.

Converting User data

User data following each BRIV (including the ADSD, but excluding RETRIEVE data) is converted in the AOR using the GCHARS and GCODES values defined for the facilitylike terminal that was used as a template to build the bridge facility. You should define these values appropriately for your client program, and specify the facilitylike name in your Link3270 call if you are not using the default. The client codepage must be specified in value 2 of CGCSGID in the AOR as well as in the DFHCNV conversion table in the router region..

The codepage conversion for user data is based on the codepage conversion for EPI emulation. Refer to in CICS Family: Communicating from CICS on System/390 for the correct values for the CGCSGID field in the TYPETERM definition associated with the facilitylike.

CGCSGID values 1 and 2 can be retrieved by an application program using EXEC CICS ASSIGN GCHARS and EXEC CICS ASSIGN GCODES respectively.

Note:
SEND TEXT NOEDIT data is always converted as if it were in 3270 data stream format.

Related concepts
The Link3270 bridge mechanism
Link3270 programming considerations
Related tasks
Establish Link3270 suitability
Using the Link3270 bridge
Writing the Link3270 client
Using Link3270 messages
Using Link3270 single transaction mode
Using Link3270 session mode
Calling the Link3270 bridge
Related reference
Link3270 message formats
Link3270 diagnostics
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