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 a distributed program link
(DPL) requests over them. The multiregion operation (MRO) facility
of CICS interregion communication (IRC) supports these requests,
and each pipe maps onto one MRO session, where the client program
represents the sending process and the CICS server region represents
the receiving process. There is a default limit of 100 pipes
for each EXCI address space.
You can 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, described in this section, is LOGONLIM. Code the parameter in columns 1 through 71 of the DFHSSIyy member, for example:
LOGONLIM=200
If the parameter is omitted, or the value specified lies outside the allowed range, then CICS will assume a limit of 100. You should code the parameter only if you want to increase the limit from the default value of 100.
CICS will publish the limit if it is determined during subsystem initialization. It will do so by creating a system level name token pair formatted as follows:
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
Bytes 4-15: Reserved, set to nulls
You can use the
callable service, IEANTRT, to retrieve the token. To
do this, invoke IEANTRT with level IEANT_SYSTEM_LEVEL (EQU 4).
The
return code is interpreted as follows:
Any other value indicates that the callable service has detected an error.
You can 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 DFHSSIyy member other than the DFHSSI00 member, you must specify DFHSSIyy in the IEFSSNaa member in the SYS1.PARMLIB library used to define CICS as an MVS subsystem.
The default EXCI pipe allocation initialization parameter defined in the DFHSSIN routine is LOGONLIM=100. You should code the parameter only if you want to increase the limit from the default of 100.