Other session parameters

The following additional operands of the DEFINE CONNECTION and DEFINE SESSIONS commands are also significant for CICS®-IMS sessions.

SENDSIZE
  • If CICS is the primary half session, specifies the maximum request unit (RU) that CICS sends to the remote IMS system. This value must be less than or equal to the value specified by the RECANY parameter in the IMS COMM macro.
  • If CICS is the secondary half session, specifies the maximum RU that CICS receives from the remote IMS system. This value must be less than or equal to the value specified by the OUTBUF parameter in the IMS TERMINAL macro.
RECEIVESIZE
  • If CICS is the primary half session, specifies the maximum request unit (RU) that CICS receives from the remote IMS system. This value must be less than or equal to the value specified by the OUTBUF parameter in the IMS TERMINAL macro.
  • If CICS is the secondary half session, specifies the maximum RU that CICS sends to the remote IMS system. This value must be less than or equal to the value specified by the RECANY parameter in the IMS COMM macro.
BUILDCHAIN(N|Y)
Specifies whether multiple RU chains are to be assembled before being passed to the application program. If Y is specified, a complete chain is passed to the application program in response to each RECEIVE command, and the application must perform any required deblocking. If N is specified, a single RU is passed to the application program in response to each RECEIVE command.
Recommendation: BUILDCHAIN(Y) is recommended, even when IMS record mode (VLVB) is used, because the logical records produced as IMS output might not coincide with RU boundaries.
DATASTREAM(USER)
Specifies a data stream profile when CICS is communicating with IMS using the START command (asynchronous processing). CICS messages generated by the START command always cause IMS to interpret the data stream profile as input for component 1. This parameter is required.

The data stream profile for distributed transaction processing can be specified by the application program using the DATASTR option of the BUILD ATTACH command.

RECORDFORMAT(U|VB)
Specifies the type of chaining that CICS is to use for transmissions that are initiated by START commands (asynchronous processing) on a particular session.
Two types of data handling algorithms are supported between CICS and IMS:
  • Chained

    Messages are sent as SNA chains. The user can use private blocking and deblocking algorithms. This format corresponds to RECORDFORMAT(U). When IMS is the receiver, a chain of RUs is interpreted as the complete single-segment message.

  • Variable length variable blocked records (VLVB)

    Messages are sent in variable-length variable-blocked format with a halfword length field before each record. This format corresponds to RECORDFORMAT(VB). When IMS is the receiver, the input deblocked element is treated as the input segment.

The data stream format for distributed transaction processing can be specified by the application program using the RECFM option of the BUILD ATTACH command.

SENDCOUNT and RECEIVECOUNT
These operands are used to specify whether the session is a SEND session or a RECEIVE session. (In macro-level definition, this is specified in the SESTYPE=SEND|RECEIVE operand.)
A SEND session is one in which the local CICS is secondary and is the contention winner. It is specified by: 
SENDCOUNT(1)
RECEIVECOUNT(0)
A RECEIVE session is one in which the local CICS is primary and is the contention loser. It is specified by: 
SENDCOUNT(0)
RECEIVECOUNT(1)
Recommendation: SEND sessions are recommended for all CICS-IMS sessions.

You need not specify a SENDPFX or a RECEIVEPFX; the name of the session is taken from the SESSNAME operand.

The following table shows the relationship between the CICS Resource Definition Online and IMS definitions of an ISC link. Related operands are shown by numbers. If CICS is communicating with an XRF IMS, NETNAME(SYSIMS) should be the USERVAR or MNPS ACB associated with the XRF IMS.

Table 1. Defining compatible CICS and IMS nodes: RDO
CICS IMS 
DFHIST  TYPE=CSECT
       ,SYSIDNT=CICL
       ,APPLID=SYSCICS  1 

DEFINE
   CONNECTION(IMSR)     3 
   GROUP(group_name)
   NETNAME(SYSIMS)      2 
   ACCESSMETHOD(VTAM)
   PROTOCOL(LU61)
   DATASTREAM(USER)

DEFINE
   SESSIONS(csdname)
   GROUP(group_name)
   PROTOCOL(LU61)      4 
   SESSNAME(IMS1)
   CONNECTION(IMSR)    3 
   NETNAMEQ(CIC1)      5 
   SENDCOUNT(1)
   RECEIVECOUNT(0)
       SENDSIZE(mmm)       7 
   RECEIVESIZE(nnn)    8 
   IOAREALEN(nnn,16364)

DEFINE
   SESSIONS(csdname)
   GROUP(group_name)
   PROTOCOL(LU61)      4 
   SESSNAME(IMS2)
   CONNECTION(IMSR)    3 
   NETNAMEQ(CIC2)      9 
   SENDCOUNT(1)
   RECEIVECOUNT(0)
       SENDSIZE(mmm)       7 
   RECEIVESIZE(nnn)    8 
   IOAREALEN(nnn,16364)
 
COMM     APPLID=SYSIMS    2 
         RECANY=mmm + 22  7 
         EDTNAME=ISCEDT

TYPE     UNITYPE=LUTYPE6  4 

TERMINAL NAME=SYSCICS     1 
         SESSION=2
         COMPT1=
         COMPT2=
         OUTBUF=nnn       8 




VTAMPOOL 

SUBPOOL NAME=CIC1         5 

NAME    CICLT1 COMPT=1      

NAME    CICLT1A




SUBPOOL NAME=CIC2         9 

NAME    CICLT2 COMPT=2

The following table shows the relationship between the CICS macro-level definitions and IMS definitions of an ISC link. Related operands are shown by numbers. NETNAME=SYSIMS should be the USERVAR or MNPS ACB associated with the IMS system if you are defining a CICS to XRF IMS session.

Table 2. Defining compatible CICS and IMS nodes: macro level
CICS IMS 
DFHIST  TYPE=CSECT
       ,SYSIDNT=CICL
       ,APPLID=SYSCICS  1 

DFHTCT TYPE=SYSTEM
      ,ACCMETH=VTAM
      ,SYSIDNT=IMSR     3 
      ,NETNAME=SYSIMS   2 

DFHTCT TYPE=TERMINAL
      ,TRMTYPE=LUTYPE6  4 
      ,TRMIDNT=IMS1
      ,SYSIDNT=IMSR     3 
      ,NETNAMEQ=CIC1    5 
      ,SESTYPE=SEND
      ,BUFFER=mmm       7 
      ,RUSIZE=nnn       8 
      ,TIOAL=(nnn,16364)
      ,DATASTR=USER

DFHTCT TYPE=TERMINAL
      ,TRMTYPE=LUTYPE6  4 
      ,TRMIDNT=IMS2
      ,SYSIDNT=IMSR     3 
      ,NETNAMEQ=CIC2    9 
      ,SESTYPE=SEND
      ,BUFFER=mmm       7 
      ,RUSIZE=nnn       8 
      ,TIOAL=(nnn,16364)
      ,DATASTR=USER
 
COMM     APPLID=SYSIMS    2 
         RECANY=mmm + 22  7 
         EDTNAME=ISCEDT

TYPE     UNITYPE=LUTYPE6  4 

TERMINAL NAME=SYSCICS     1 
         SESSION=2
         COMPT1=
         COMPT2=
         OUTBUF=nnn       8 

VTAMPOOL 

SUBPOOL NAME=CIC1         5 

NAME    CICLT1 COMPT=1      

NAME    CICLT1A


SUBPOOL NAME=CIC2         9 

NAME    CICLT2 COMPT=2