EXCI pipe allocation

The external CICS interface is an application programming interface that enables a non-CICS program (a client program) running in MVS to call a program (a server program) running in a CICS region and to pass and receive data by means of a communications area.

The CICS application is invoked as though it is linked to by another CICS application program.

This programming interface allows a user to allocate and open sessions or pipes which operate in "half-duplex", flip-flop" mode, to a CICS region and to pass distributed program link requests over them. The multiregion operation facility of CICS interregion communication supports these requests, and each pipe maps onto one MRO session, in which the client program represents the sending process and the CICS server region represents the receiving process. A default limit of 100 pipes for each EXCI address space applies.

Specifying the EXCI pipe allocation limit

Specify the EXCI pipe allocation limit for the CICS subsystem in a member DFHSSIyy of the SYS1.PARMLIB library, where yy is the suffix that identifies the SYS1.PARMLIB member used to define the CICS subsystem. The parameter is LOGONLIM.

Code the parameter in columns 1 through 71 of the DFHSSIyy member, like this:
			LOGONLIM=200
LOGONLIM=nn
The minimum and maximum values that can be specified for nn are 100 and 250.

If you omit the parameter or the value specified lies outside the allowed range, CICS assumes a limit of 100.

The EXCI pipe allocation limit

CICS publishes the limit if it is determined during subsystem initialization, by creating a system-level name token pair formatted like this:
    Name: input, fixed length 16 byte type      
      Bytes 0-7 : The character string 'DFHIRP '      
      Bytes 8-15: The character string 'LOGONLIM'     
    Token: output, fixed length 16 byte type      
      Bytes 0-3 : The logon limit, held as fullword binary file     
      Bytes 4-15: Reserved, set to nulls
You can use the callable service, IEANTRT, to retrieve the token. Invoke IEANTRT with level IEANT_SYSTEM_LEVEL (EQU 4). The return code is interpreted in the following way:
0
The name and token pair exists and the token has been retrieved. The logon limit can be extracted from the token.
4
The name and token pair does not exist. The logon limit is assumed to be 100.
Any other value indicates that the callable service has detected an error.

Default EXCI pipe allocation limit initialization parameter

Define the EXCI pipe allocation limit parameter for the CICS subsystem in a member DFHSSIyy of the SYS1.PARMLIB library.

To use parameters defined in any DFHSSIyy member except the DFHSSI00 member, specify DFHSSIyy in the IEFSSNaa member in the SYS1.PARMLIB library used to define CICS as an MVS subsystem. For more information on IEFSSNaa, see Coding the IEFSSNaa MVS subsystem initialization member.
  • If you do not specify DFHSSIyy, the DFHSSIN routine tries to use the parameters that are defined in the DFHSSI00 member.
  • If the DFHSSI00 member does not exist, the DFHSSIN routine uses the default parameters that are defined in the DFHSSIN routine.
  • If you specify DFHSSIyy but it does not exist, the DFHSSIN routine uses the default parameters that are defined in the DFHSSIN routine.
The default EXCI pipe allocation initialization parameter defined in the DFHSSIN routine is LOGONLIM=100.