6. To complete the connection, the program in virtual machine Y issues a CMSIUCV ACCEPT. By issuing CMSIUCV ACCEPT, CMS invokes the IUCV ACCEPT function. This completes the IUCV communication link with
virtual machine X. The CMSIUCV ACCEPT also associates the exit address, "2", with the pathid.
7. Virtual machine X receives a connection-complete external interrupt as a result
of the CMSIUCV ACCEPT issued by the program in virtual machine Y.
8. "EXIT B" receives control as a result of the external interrupt. ("EXIT B"
receives control because it is specified on the EXIT parameter of the CMSIUCV macro.)
9. Virtual machine X completed its communications with virtual machine Y and
terminates the lUCY communication link. The program in virtual machine X
issues an CMSIUCV SEVER to terminate this link. By issuing CMSIUCV SEVER, CMS invokes the IUCV SEVER function and clears the exit associ­
ated with the communication link. 10. Virtual machine Y receives a SEVER external interrupt as a result of the CMSIUCV SEVER issued by virtual machine X.
11. "EXIT 2" receives control as a result of the external interrupt. ("EXIT 2"
receives control because it was specified on the EXIT parameter of the CMSIUCV macro.)
12. The program in virtual machine Y issues a CMSIUCV SEVER to terminate the
communication link. By issuing CMSIUCV SEVER, CMS invokes the IUCV SEVER function and clears the exit associated with the communication link.
13. After all communications are complete and all communication paths have been
SEVERed, the program in virtual machine X and the program in virtual
machine Y independently issue HNDIUCV CLR. HNDIUCV CLR terminates IUCV communications and clears the general exit for IUCV PENDING CONNECTs. CMS invokes the IUCV RETRIEVE BUFFER function if there
are no other programs in the virtual machine using IUCV. 14. This is the label specified in the NAME parameter. This location contains the
identifying name of the program in virtual machine X. The name of this pro­
gram is RED.
15. This is the label specified in the NAME parameter. This location contains the
identifying name of the program in virtual machine Y. The name of this pro­
gram is BLUE. Guidelines and Limitations of the CMS IV CV Support
Some of the existing IUCV functions affect the IUCV environment of the entire
virtual machine. Since CMS cannot intercept any IUCV functions directly issued
by a program, any program using the CMS IUCV support has certain limitations on
its use of IUCV functions. The program must not issue any IUCV function that
alters the virtual machine's IUCV environment.
The following is a list of IUCV functions. The list describes their relationship to
the CMS IUCV support and some guidelines for their usage. If any functions listed
CMS IUCV Support 367

as "Should not be used" are indeed used, other programs using CMS IUCV func­
tions in the virtual machine may be affected. For information on coding the follow­
ing functions, see the "Inter-User Communications Vehicle" earlier in this manual.
ACCEPT
is invoked by a program via the CMSIUCV macro. It should not be issued
directly by a program. CONNECT is invoked by a program via the CMSIUCV macro. It should not be issued
directly by a program.
DECLARE BUFFER
is used by HNDIUCV to initialize the virtual machine's IUCV environment.
It should not be issued directly by a program.
DESCRIBE
should not be used because this function clears the pending-message external
interruption for the described message. This interrupt may not belong to the
issuer of the DESCRIBE function. Thus, other programs running in the
same virtual machine may be affected since the message is lost and never
reflected to the true target.
PURGE
is issued directly by a program.
QUERY
is used by HNDIUCV to determine the size of the external interrupt buffer
and the maximum number of connections for this virtual machine. It may be
issued directly by an application program.
QUIESCE
is issued directly by a program to quiesce a specific path. However, the
issuer must be careful that the IP ALL bit is not turned on in the IPFLAGS 1
byte of the parameter list. This would quiesce all paths in the virtual
machine.
RECEIVE
is issued directly by the application program. However, the issuer must be
careful that a specific message id or path id is specified in the IUCV parame­
ter list. If it is not, IUCV RECEIVEs the first message that has not yet been
partially received for the entire virtual machine. This message may not
belong to the program that issued the IUCV RECEIVE.
REJECT
is issued directly by a program.
REPLY
is issued directly by a program.
RESUME
368 VM/SP System Programmer's Guide
is issued directly by a program in order to resume a specific path. However,
the issuer must be careful that the IP ALL bit is not turned on in the
IPFLAGS 1 byte of the parameter list. This would resume all paths in the
virtual machine.