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Former Member

READ mode and CACHE mode of queries.

Hello All,

I have read about the read mode and cachemode regarding transaction RSRT. Could you please give me examples for the different kind of read modes and cachemode so that I can understand it better.

I could not get an idea of the data transfer between the database and OLAP for the read modes.

thanks in advance

amit

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  • author's profile photo Former Member
    Former Member
    Posted on Jan 09, 2005 at 04:56 PM

    The read mode determines how much data is read in one go. Read mode A "all" means that data is read for all possible navigations at the first navigation. H means that data is only read at demand, just the data that's needed for the current navigation. X is intermediate, on demand for normal navigation, all for hierarchies. A means usually more data is read from the database is needs to be kept in the application server. H means least possible amount of data.

    The Cachemodes determines whereto the OLAP Cache entries are written (to memory, with possible swapping, or directly to persistent storage which is file or database table). An OLAP Cache entry is a result set of a query navigation that is stored for future usage (if the same or very similar navigation is done again). BTW, there is no dependency or connection between Cache mode and read mode (frequently misunderstood feature).

    Cheers, Klaus

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    • Former Member Former Member

      Please see below what online documentation reveals.

      1. could be used if the amount of data is significantly reduced by the filters.

      2. is only there for testing in RSRT, the real settings needs to be done in the key figure properties. More accuracy, less performance.

      I am not sure about 3., probably more debugging than performance related. Looking for more info, will update this message once I've got it.

      Optimization is useful for large queries (handling much data). Memory will be allocated more efficiently (at the start, rather than incrementally), if subsequent execution need similar amount of memory. The frequency of optimization is determined by optimization mode.

      Documentation:

      Using the selection of structure elements

      The using the selection of structure elements option can be selected for any query but is only really useful in a couple of cases.

      In queries, selections are frequently defined on one or more characteristics in the columns, or more precisely in the structure elements. One or more of these structure elements are often filtered in the BEx Analyzer or in Web applications. If you do not select the using a selection of structure elements option these dynamic (structure element) selections are not transferred to the database. Normally the data for the entire structure or for both structures is then read from the database.

      Accuracy

      You can specify the accuracy with which a key figure needs to be calculated in the InfoObject maintenance.

      You can only specify the accuracy with which all query key figures need to be calculated in the Query Monitor (and not in the BEx Query Designer in the BW front end). You can use this to “override” the settings made in InfoObject maintenance for individual key figures, where necessary.

      Optimization mode

      If you do not make any other settings the OLAP processor determines the optimal initial size of the table SP, that is the memory structure in which data is held and processed in the OLAP processor (see Cache Structure). This is done after the first execution and again after a period of 31 days since the last optimization. It automatically generates a report afterwards.

      In the Query Properties dialog box in the Query Monitor you can implement, modify of deactivate this function. Choose one of the following options:

      · Query is optimized after generation (0)

      · Query optimization with individual periods in days (1) Here you can determine the optimization period yourself.

      · Query optimization inactive (9)

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