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Annotation of loncom/html/adm/help/tex/Caching.tex, revision 1.1

1.1     ! www         1: \label{Caching}
        !             2: LON-CAPA does not serve static web pages, but generates pages and other 
        !             3: resources dynamically and adaptively based on a large number of data input
        !             4: sources, such as the user preference, the course environment, maps, etc.
        !             5: 
        !             6: Since LON-CAPA also has to sustain large workloads, it is 
        !             7: prohibitive to gather, compile, and process these data for every single
        !             8: access, when in the vast majority of cases, nothing has changed between the
        !             9: current and previous requests.
        !            10: 
        !            11: LON-CAPA thus caches data. There are basically two different 
        !            12: \textbf{caching mechanisms\index{caching mechanisms}}, which LON-CAPA uses:
        !            13: 
        !            14: \begin{itemize}
        !            15: \item Caching at \textbf{course initialization\index{course initialization}}:
        !            16: Several sources of data are compiled when a user enters a course during a 
        !            17: session. An example is the table of contents (DOCS/NAV) for the course - 
        !            18: if you change DOCS, you need
        !            19: to re-enter (``\textbf{re-initialize}'') the course in order to see the 
        !            20: effects.
        !            21: 
        !            22: The course environment (PARM/Course Environment) in general also only gets 
        !            23: evaluated when entering a course, and while it does get re-evaluated for your
        !            24: session whenever you change anything, it - like DOCS changes - will not 
        !            25: immediately take effect for
        !            26: other users currently working in the course. So if for example you disable
        !            27: course discussion, users will only be prevented from discussion when they 
        !            28: enter the course the next time. 
        !            29: 
        !            30: \item Caching of \textbf{assessment parameters\index{assessment parameters}}:
        !            31: Data such as the deadline of homework problems, and the text of Simple 
        !            32: Problems, is only re-read \textbf{every ten minutes}. It can thus happen that
        !            33: you open up a homework problem in PARM, but for another ten minutes, some 
        !            34: students cannot access it. Also changes to Simple Problems will not immediately
        !            35: take effect for all users (including yourself).
        !            36: \end{itemize}
        !            37:  
        !            38: It is important to be aware of these mechanisms, since otherwise results can
        !            39: be confusing (``Didn't I just change this???'').