MODIFY LL2 command


Start a continuous link level 2 test:

>>-MODIFY-- --procname--,--LL2--,--ID--=--name------------------>

>--,--OPTION--=--CONT--+------------------+--------------------->
                       '-,--DATA--=--data-'   

   .-,--NFRAMES--=--1-----------------------.   
>--+----------------------------------------+------------------><
   '-,--NFRAMES--=--number_of_test_messages-'


Start a brief link level 2 test:

>>-MODIFY-- --procname--,--LL2--,--ID--=--name------------------>

>--+------------------+----------------------------------------->
   '-,--DATA--=--data-'   

   .-,--NFRAMES--=--1-----------------------.   
>--+----------------------------------------+------------------->
   '-,--NFRAMES--=--number_of_test_messages-'   

   .-,--NTRANS--=--10----------------------.   
>--+---------------------------------------+-------------------><
   '-,--NTRANS--=--number_of_test_messages-'


Stop a link level 2 test:

>>-MODIFY-- --procname--,--LL2--,--ID--=--name------------------>

>--,--OPTION--=--CANCEL----------------------------------------><

Abbreviations

Operand	Abbreviation
MODIFY	F
OPTION=CANCEL	OPT=CANCEL or CANCEL
OPTION=CONT	OPT=CONT or CONT

Purpose

The MODIFY LL2 command is used to request a link level 2 test for a nonswitched SDLC link. This tests communication lines between the following link ends:

An NCP and a peripheral PU attached to it.
Two NCPs (PU type 4).
VTAM® and a peripheral PU attached to it.
An NCP and another VTAM (PU type 5). The command must be initiated from the NCP's domain, and the link station identified by the ID operand must be inactive or inoperative.
VTAM and another VTAM (PU type 5). The command must be initiated from the VTAM with the highest subarea, and the link station identified by the ID operand must be inactive or inoperative.

The test is performed by sending test data over the link from the primary end of the line to the remote station; the data is then echoed back to the sender. The data received is compared with the data sent. VTAM collects the results and displays these results in a message. For more information about when and how to run an LL2 test, see z/OS Communications Server: SNA Diagnosis Vol 1, Techniques and Procedures.

Operands

procname

The procedure name for the command. If procname in the START command was specified as startname.ident, where startname is the VTAM start procedure and ident is the optional identifier, either startname.ident or ident can be specified for procname.

If procname in the START command was startname, startname must be specified for procname.

DATA=data

Specifies optional user data to be used as part of the test message. Any EBCDIC alphabetic, numeric, or special characters (such as @ # $) can be specified. The maximum number of characters permitted depends on the characteristics of the device at the receiving end of the test. If the DATA operand is omitted, VTAM sends test messages without user data.

If DATA is specified and the physical unit returns the correct number of echoes but does not return any data, the physical unit probably does not support echo check with data. To determine whether a physical unit supports data, see the component description for that physical unit.

ID=name

Specifies:

For a test of an SDLC link:
- Between two NCPs or
- Between an NCP and a host processor or
- Between two host processors
the name of a link station on the link that is to be tested. The specified link station must be in the NCP or the host that is to initiate the test. The link station at the originating end must be inactive.
For a link to an SDLC peripheral node:
the name of a physical unit on the link that is to be tested. The SDLC link must be active and the specified physical unit must be inactive, but, for a multipoint link, the other physical units on the link can be active during the test.

If there is a conflict between VTAM and the NCP about whether a resource has been dynamically reconfigured, an informational message is displayed. This could happen when an NCP is shared among VTAMs.

See z/OS Communications Server: SNA Diagnosis Vol 1, Techniques and Procedures for additional information about testing a nonswitched SDLC communication line.

NFRAMES=number_of_test_messages

Specifies (for a multipoint line) the number of test messages to send to the physical unit each time its station is selected. This option allows the test messages to be interleaved with other data going to other stations on the line. Specify any decimal integer 1–65535. The default is 1.

NTRANS=number_of_test_messages

Specifies the number of test messages to send. This number can be any decimal integer 1–65535. (Specifying NTRANS=65535 gives the same result as specifying OPTION=CONT.)

NTRANS must not be specified on the same command as the OPTION operand. If neither NTRANS nor OPTION is specified, the default, NTRANS=10, is used.

OPTION

Specifies a test option to use instead of the NTRANS value. If OPTION is not specified, the value in effect for NTRANS is used. OPTION must not be specified on the same command with the NTRANS operand.

OPTION=CANCEL: Specifies that the test running currently should be stopped.
OPTION=CONT: Specifies that the test being started should run continuously until canceled by the VTAM operator.