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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

2114.0. "An "internal" question..." by TAEC::HARPER (John Harper, DTN 830 3647) Wed Jan 15 1992 07:34

    I have a question about the "internals" which just occurred to me.
    
    As I understand the Performance FM, what happens is that when you do a
    SHOW (say) for one of its computed statistics, it gets the necessary
    base data from the base AM using two SHOWs, then calculates the
    statistic you asked for and gives it to you.
    
    What I don't understand is how this request gets routed within MCC.
    Clearly the base AM has set up a dispatch table saying it knows how to
    deal with (say) SHOW NODE4 type of stuff.  Does the Perf FM also say
    this? And if so how does the internal router know who to give which
    kind of request?
    
    Or does it all go to the base AM, which then sends stuff it can't
    handle to Perf?  But if so, how does it know to do this?
    
    Or is there some kind of multicast, with all but one of the requested
    MMs saying "huh?" and subsequently being ignored?
    
    Or is there something else that I'm missing?
    
    	John
    
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2114.1how dispatching occursTOOK::CALLANDERMCC = My Constant CompanionWed Jan 15 1992 11:0021
    
    The internals of MCC are set up to dispatch based on 3 items. These are
    the command (Verb), the entity (Class/subclass...), and the partition
    (attribute or event).
    
    The show command is what is called an examine directive. The PA module
    enrolls in the function module dispatch table an entry for the
    SHOW/*/STATISTICS commands, while the access modules register into the
    access module dispatch table entries for SHOW/*/? (where ? equals one
    entry for each partition supported by the AM).
    
    When and mcc_call_function is performed (this is what the PMs do), then
    the functional tables are always searched for a dispatch match before
    searching the access table. If an mcc_call_access is done, then only
    the access table is searched.
    
    If this unclear there is more information on this subject in the SRM
    chapter 4 and 10 (section 10.5).
    
    jill