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Wait# 45 nam='db file scattered read'

Discussion in 'Server Administration and Options' started by aayan_110, Jan 16, 2011.

  1. aayan_110

    aayan_110 Active Member

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    Hi Guyz

    One of my setup screen in my Oracle Financials Application was running very slow while querying, updatin ,& saving.
    When i checked the trace file it showing me msg

    Wait# 45 nam='db file scattered read'

    how to solve this , can you answer me in detail, your help would be appreciated.

    thanks
     
  2. prashant

    prashant Forum Advisor

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    Hi,

    db file scattered read event usually occurs for full table scan, since table scan is 'scattered' as opposed to index scan (sequential).

    Full table scan can happen in a lot of cases:-

    1) No index on where clause columns
    2) Stale statistics
    3) Proper statistics for a very small table (FTS is preffered)
    4) init.ora parameters like 'db_file_multiblock_read_count', 'optimizer_index_caching' etc.

    I would advise you to take a tkprof of the trace file to get a more clear picture.

    You can use following command for the same:-

    tkprof <trace_file_name>.trc output_file.prf sys=no waits=yes sort=fchela,exeela,prsela explain=schema_name/password@tns.db_domain

    This will tell us whether db scattered read is the problem which needs to be addressed. If yes what is the query, its explain plan etc.

    -Prashant
     
    aayan_110 likes this.