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Conference azur::mcc

Title:DECmcc user notes file. Does not replace IPMT.
Notice:Use IPMT for problems. Newsletter location in note 6187
Moderator:TAEC::BEROUD
Created:Mon Aug 21 1989
Last Modified:Wed Jun 04 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:6497
Total number of notes:27359

967.0. "DAP Unsupported DELETE CLASS ?" by RIVAGE::HAYES (A European Telecomet ...) Mon Apr 29 1991 05:19

    
    	Hello,
    
    
    	We here use the DAP> DELETE CLASS <entity> to create
    	bigger dictionaries than the development one but
    	smaller than the system-wide one .
    
    	Our partners exactly have the same need as we have to
    	create those intermediate dictionaries (containing the iconic
    	map/Domain FM for example ...)
    
    	Will the command DELETE CLASS in the future versions be :
    
    		1- Documented, working ?
    		2- Undocumented working ?
    		3- Undocumented, not working ?
    
    	The last is of course the worst for us, so in case 3- would
    	something work to create such intermediate/customizable dictionaries ?.
    
    	Thanks for your help
    
    
     		Catherine
    		
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967.1DELETEing Dictionary information can be dangerousTOOK::GUERTINI do this for a living -- reallyMon Apr 29 1991 10:5315
    Catherine,
    
       We felt, after much back and forth discussion, that the DAP DELETE
    CLASS command was too destructive to document.  We were concerned at
    fieldtest that customers (in particular end-users) could easily wipe
    out a major portion of their dictionary.  The DAP program has no error
    recovery or confirm-delete capability.  We knew that developers would
    have a problem, however, we felt that the UPDATE command would be able
    to provide the needed capabilities (in fact, it DELETEs and then
    LOADs). 
    
    If you need information about future DAP functionality, please contact
    the Project Leader for the MCC Toolkit team, Darryl Black (MKNME::BLACK).
    
    -Matt.
967.2one MSL developer's concerns, as sent to DarrylCOOKIE::KITTELLRichard - Architected Info MgmtMon Apr 29 1991 12:4938
        Darryl,

        Hi, I wanted to respond to an issue raised in note 967 of the
        MCC conference regarding support of the delete command.

        I don't have an opinion as to whether DELETE CLASS
        specifically should remain an accepted DAP command. But I do
        have a concern that a specific capability be available. That
        is the ability for an update job to "do the right thing" in
        order to leave the dictionary in the proper state, without
        knowing ahead of time what the current state is.

        The desired state of the dictionary after the job runs is that
        the dictionary have the current definitions loaded from the
        .COM file produced by the MSL compiler. If LOAD and UPDATE
        are the only DAP commands available, then the update job has
        to know whether or not the class has ever been loaded into the
        dictionary, so it knows which one to use. That is because LOAD
        fails if the class already exists in the dictionary, and UPDATE
        fails if it doesn't.

        I currently have our update job use a DELETE in one DAP
        invocation followed by a LOAD in another DAP invocation. The
        job ignores the completion status of the DELETE invocation.
        This sequence produces the desired result regardless of the
        prior state of the dictionary. If you remove DELETE, is there
        a way to have the update job do the right thing?

        Perhaps you might modify UPDATE so it optionally deletes the
        class if it is already there, but doesn't complain if it
        isn't. That would give us the same capability, without
        exposing DELETE CLASS to the user.
        
        Thanks for considering this issue,

        Richard Kittell
        AIM Engineering
967.3DFLAT::PLOUFFEJerryMon Apr 29 1991 14:4323
RE: .0

  Catherine:

    Hello.  I discussed your question w/ Darryl and he the net result is that
    the DELETE command will remain working--though undocumented for all the 
    reasons that Matt mentioned in .1.  This decision will most likely be 
    revisited (along with other key DAP interface issues) in v2.0.  We will
    keep your need in mind.  Thanks for informing us of your use of this
    command.

RE: .2

  Richard:

    I agree with your assessment of the need "to do the right thing".  I will
    put this on the DAP to do list.

                                         - Jerry

                                           Current member of the Toolkit Team
                                           working on DAP...