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<title>Work with multiple device display files</title>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Work with multiple device display files</h1>
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<div><p>The normal mode of operation on a system is for the workstation
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user to sign on and become the requester for an interactive job. Many users
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can do this at the same time, because each will use a logical copy of the
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procedure, including the display file in the procedure. Each requester calls
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a separate job in this kind of use. This is not considered to be multiple
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device display use.</p>
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<div class="section"> <p>A multiple device display configuration occurs when a single
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job called by one requester communicates with multiple display stations through
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one display file. While only one display file can be handled by a CL procedure,
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the display file, or different record formats within it, can be sent to several
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device displays. Commands used primarily with multiple device display files
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are:</p>
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<dl><dt class="dlterm"><span class="cmdname">End Receive (ENDRCV)</span></dt>
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<dd>This command cancels requests for input that have not been satisfied.</dd>
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<dt class="dlterm"><span class="cmdname">Wait (WAIT)</span></dt>
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<dd>Accepts input from any device display from which user data was requested
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by one or more previous <span class="cmdname">Receive File (RCVF)</span> or SNDRCVF
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commands when WAIT(*NO) was specified on the command, or by one or more previous <span class="cmdname">Send
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File (SNDF)</span> commands to a record format containing the INVITE DDS
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keyword.</dd>
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</dl>
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<p>If you use a multiple device display file, the device names
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must be specified on the DEV parameter on the CRTDSPF command when the display
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file is created, on the CHGDSPF command when the display file is changed,
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or on an override command, and the number of devices must be less than or
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equal to the number specified on the MAXDEV parameter on the CRTDSPF command.</p>
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<p>Multiple
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device display configurations affect the <span class="cmdname">Send/Receive File (SNDRCVF)</span> and
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the RCVF commands and you may need to use the <span class="cmdname">Wait (WAIT)</span> or <span class="cmdname">End
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Receive (ENDRCV)</span> commands. When an <span class="cmdname">Receive File (RCVF)</span> or <span class="cmdname">Send/Receive
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File (SNDRCVF)</span> command is used with multiple display devices, the
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default value WAIT(*YES) prevents further processing until an input-capable
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field is returned to the program from the device named on the DEV parameter.
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Because the response may be delayed, it is sometimes useful
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to specify WAIT(*NO), thus letting your procedure or program continue running
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other commands before the receive operation is satisfied.</p>
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<p>If you use
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an RCVF or <span class="cmdname">Send/Receive File (SNDRCVF)</span> command and specify
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WAIT(*NO), the CL procedure or program continues running until a <span class="cmdname">Wait
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(WAIT)</span> command is processed.</p>
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<p>Using a <span class="cmdname">Send File (SNDF)</span> command
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with a record format which has the DDS INVITE keyword is equivalent to using
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a <span class="cmdname">Send/Receive File (SNDRCVF)</span> command with WAIT(*NO) specified.
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The DDS INVITE keyword is ignored for <span class="cmdname">Send/Receive File (SNDRCVF)</span> and <span class="cmdname">Receive
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File (RCVF)</span> commands.</p>
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<p>The <span class="cmdname">Wait (WAIT)</span> command
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must be issued to access a data record. If no data is available, processing
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is suspended until data is received from a device display or until the time
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limit specified in the WAITRCD parameter for the display file on the CRTDSPF,
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CHGDSPF, or OVRDSPF commands has passed. If the time limit passes, message
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CPF0889 is issued.</p>
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<p>The <span class="cmdname">Wait (WAIT)</span> will also be satisfied
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by the job being canceled with the controlled option on the ENDJOB, ENDSYS,
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PWRDWNSYS, and ENDSBS commands. In this case, message CPF0888 is issued and
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no data is returned. If a WAIT command is issued without a preceding receive
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request (such as RCVF . . . WAIT(*NO)), a processing error occurs.</p>
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<p>A
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typical multiple device display configuration (with code) might look like
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this:</p>
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<br /><img src="rbafn506.gif" alt="Example of a typical multiple device display configuration (with code)." /><br /><p>In the above example, the
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first two commands show a typical sequence in which the default is taken;
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processing waits for the receive operation from WS2 to complete. Because
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WS2 is specified on the DEV parameter, the RCVF command does not run until
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WS2 responds, even if prior outstanding requests (not shown) from other stations
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are satisfied.</p>
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<p>The SNDRCVF command, however, has WAIT(*NO) specified
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and so does not wait for a response from WS1. Instead, processing continues
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and PROGA is called. Processing then stops at the WAIT command until an outstanding
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request is satisfied by a workstation, or until the function reaches time-out.</p>
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<p>The
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WAIT command has the following format: </p>
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<pre>WAIT DEV(CL-variable-name)</pre>
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<p>If the DEV parameter is specified, the CL variable name is
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the name of the device that responded. (The default is *NONE.) If there are
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several receive requests (such as RCVF. . . WAIT(*NO)), this variable takes
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the name of the first device to respond after the <span class="cmdname">Wait (WAIT)</span> command
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is encountered and processing continues. The data received is placed in the
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variable associated with the field in the device display.</p>
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<p>A RCVF command
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with WAIT(*YES) specified can be used to wait for data from a specific device.
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The same record format name must be specified for both the operation that
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started the receive request and the RCVF command.</p>
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<p>In some cases, several
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receive requests are outstanding, but processing cannot proceed further without
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a reply from a specific device display. In the following example, three commands
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specify WAIT(*NO), but processing cannot continue at label LOOP until WS3
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replies: </p>
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<pre> PGM
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.
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.
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.
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SNDF DEV(WS1) RCDFMT(ONE)
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SNDF DEV(WS2) RCDFMT(TWO)
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SNDRCVF DEV(WS3) RCDFMT(THREE) WAIT(*NO)
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RCVF DEV(WS2) RCDFMT(TWO) WAIT(*NO)
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RCVF DEV(WS1) RCDFMT(ONE) WAIT(*NO)
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CALL...
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CALL...
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.
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.
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RCVF DEV(WS3) RCDFMT(THREE) WAIT(*YES)
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LOOP: WAIT DEV(&WSNAME)
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MONMSG CPF0882 EXEC(GOTO REPLY)
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.
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.
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.
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GOTO LOOP
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REPLY: CALL...
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.
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.
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.
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ENDPGM</pre>
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<p>CL procedures and programs also support the <span class="cmdname">End Receive
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(ENDRCV)</span> command, which lets you cancel a request for input that
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has not yet been satisfied. A <span class="cmdname">Send File (SNDF)</span> or <span class="cmdname">Send/Receive
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File (SNDRCVF)</span> command will also cancel a request for input that
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has not yet been satisfied. However, if the data was available at the time
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the <span class="cmdname">Send File (SNDF)</span> or <span class="cmdname">Send/Receive File (SNDRCVF)</span> command
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was processed, message CPF0887 is sent. In this case the data must be received
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with the WAIT command or <span class="cmdname">Receive File (RCVF)</span> command, or
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the request must be explicitly canceled with a <span class="cmdname">End Receive (ENDRCV)</span> command
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before the <span class="cmdname">Send File (SNDF)</span> or <span class="cmdname">Send/Receive File
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(SNDRCVF)</span> command can be processed.</p>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="wfile.htm" title="Two types of files are supported in CL procedures and programs: display files and database files.">Work with files in CL procedures</a></div>
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</div>
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<div class="reltasks"><strong>Related tasks</strong><br />
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<div><a href="workv.htm" title="CL procedures consist of CL commands, and the commands themselves consist of the command statement, parameters, and parameter values.">Use variables</a></div>
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</div>
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<div class="relinfo"><strong>Related information</strong><br />
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<div><a href="../cl/wait.htm">Wait (WAIT) command</a></div>
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<div><a href="../cl/endrcv.htm">End Receive (ENDRCV) command</a></div>
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<div><a href="../cl/sndf.htm">Send File (SNDF) command</a></div>
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<div><a href="../cl/rcvf.htm">Receive File (RCVF) command</a></div>
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<div><a href="../cl/sndrcvf.htm">Send/Receive File (SNDRCVF) command</a></div>
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</div>
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</div>
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</body>
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