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The following simple example shows the sequence of calls in distributed dialogs via LU6.1. In each case there are indications as to which fields can or have to be set or evaluated. The field names are specified using COBOL notation.
In this example the job-submitting program consists of two program units: in the first unit, the subjob is submitted to the job-receiving service; in the second unit, the response of the job-receiving service is read and the response is output to the terminal, if necessary.
As explained in section "Error handling by the program unit" a job-submitting program unit which follows after a synchronization point is started not only in a normal run, but also after rolling back a distributed transaction with service restart. This is why a check is made in the first unit of the job-submitting program whether status information is available. Such a service restart only occurs, however, if the job-submitting service has set a synchronization point prior to the start of this program unit (with or without participation of a job-receiving service).
1. Job-submitting program, first unit
INIT
Evaluate:
KCKNZVG --> R service restart,
status information might be available.
MGET Input message from terminal. If the job-submitting
service has already reached a synchronization point,
status information may be present as well.
Evaluate:
KCRPI --> Return information from the job receiver
blanks there is no status information present
>svid there is status information from the
job-receiving service with the specified service ID. In this case
the status information is to be read with a 2nd MGET.
2. MGET
Read the status information after which error handling is necessary.
Set:
KCOM <-- with NT
KCLA <-- with the length 0
KCRN <-- with the service ID (>svid)
KCMF <-- with blanks
Evaluate:
KCVGST --> service status:
I job-receiving service inactive
E job-receiving service terminated with PEND ER/FR
Z job-receiving service terminated by openUTM with PEND ER
R job-receiving service terminated with PEND RS
T time has expired (timer)
KCTAST --> transaction status:
I transaction in job-receiving service inactive
R transaction in job-receiving service rolled back
M mismatch
If there is no status information present:
APRO Address the job-receiving service (if not already done)
Set:
KCOM <-- with DM for dialog service
KCRN <-- with the LTAC of the job-receiving service
KCPA <-- with double-step addressing:
with the name of the partner application
KCPI <-- with a self-selected service ID (>svid)
KCLM , 0
MPUT to job-receiving service
Set:
KCOM <-- NT or NE
KCRN <-- with the service ID (>svid)
KCMF <-- possible format ID for job-receiver
KCDF <-- binary 0
KCLM <-- length
PEND (end of first unit)
Set:
KCOM <-- PEND call variant:
KP normally recommended in the job-submitting
service
RE end of transaction is requested
FI not allowed because job-receiver still open
ER/FR also aborts job-receiving service
PA prohibited after MPUT to job-receiving service
PR prohibited after MPUT to job-receiving service
SP prohibited after MPUT to job-receiving service
FC prohibited after MPUT to job-receiving service
KCRN <-- name of follow-up program unit of job submitter
(second unit of the job-submitting program)
2. Job-receiving program
INIT
Evaluate:
KCBENID --> name of the session
KCLOGTER --> name of the partner application
KCTERMN --> ID of the partner application
KCCP --> ID of the protocol used, '1' is entered for LU6.1
KCRMF --> format ID from first MPUT of the job submitter
MGET Read message from job-submitting service
Evaluate:
KCRCCC --> KDCS error code 19Z through 39Z cannot occur
KCRLM --> length from MPUT of the job submitter (KCLM)
KCRST Byte1 --> service status of job-submitting service:
O job-submitting service is open
KCRST Byte2 --> transaction status of job-submitting service
O transaction is open (PEND KP for job submitter)
P end of transaction initiated (PEND RE)
C transaction with job submitter terminated
KCRMF if more message segments still present:
format ID of the next segment, otherwise:
format ID of segment read.
MPUT unchanged
Set:
KCOM <-- with NT or NE
KCMF <-- format ID or blanks
KCLM <-- length of the message
KCRN <-- with blanks to send the message to the job submitter
KCDF <-- any value which the job submitter receives
with MGET
PEND End of job-receiving program unit
Set:
KCOM <-- depending on the transaction status:
KP only allowed with KCTAST=O or C
RE terminates the transaction with KCTAST=P or initiates end of
transaction with KCTAST=O or C
FI end of the job-receiving service, otherwise as PEND RE
ER/FR end of the job-receiving service, transaction is rolled back, job
submitter is informed
PA/PR no special points, cannot be used to send a message to the job
submitter
KCRN <-- if necessary (with PEND KP or PEND RE), name of the follow-up
program unit of job-receiving service
3. Follow-up program unit of the job-submitting program (second unit)
INIT
Evaluate:
KCRPI <-- service ID of the job-receiving service
KCRMF <-- format ID from 1st MPUT of the job receiver
MGET Read message from the job receiver
Set:
KCOM <-- NT
KCLA <-- length of the message area
KCRN <-- service ID from KCRPI of the INIT call
KCMF <-- format ID from KCRMF of the INIT call
Evaluate:
KCRLM --> actual length of the input message
KCRMF --> if more message segments present:
format ID of next segment, otherwise:
format ID of segment read.
KCRDF --> value from the relevant MPUT of the
job-receiving service.
KCRPI --> service ID if further message
segments present
KCRST Byte1 --> service status of job-receiving service:
O job-receiving service is open
C job-receiving service is terminated (PEND FI)
KCRST Byte2 --> transaction status of job-receiving service:
O transaction is open (PEND KP)
P job receiver has requested end of transaction (with PEND RE or
FI, PTC status)
C transaction is terminated (PEND RE or FI)
MPUT to the terminal
Set:
KCRN <-- with blanks
KCOM <-- with NT or NE
KCLM <-- with the length of the message
KCMF <-- with the format ID or blanks
KCDF <-- if necessary, with a screen function
PEND end of the follow-up program unit of the job-receiving service
Set:
KCOM <-- depending on status indicators in KCRST
FI only allowed with KCVGST=C, terminates service and transaction
RE terminates the transaction with KCTAST=P, not allowed with
KCTAST=O (because message directed to terminal)
ER/FR rolls back transaction, job-receiving service is also rolled back
and terminated;
only exception: KCTAST=C and KCVGST=C.
KP not recommended if KCTAST=P
PA/PR prohibited since message was sent to terminal.
KCRN <-- if necessary (with PEND KP or PEND RE), name of the follow-up
program unit of the job-submitting service