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  1. #1
    Join Date
    Jan 2001


    I have couple of questions about the Oracle performance tuning..One of our customer has sent us the report on performance.
    I could not understand some of things that he has said.
    1.db_file_multiblock_read_count*db_block_size = number of blocks read during the full table scan which should be max CHUNK SIZE, usually 64K.
    Where can I find max CHUNK SIZE ?
    Is this true for all queries doing full tablescan ?
    Is this value should be lower or higher to check for performance ?
    Is their any way that I can find which queries doing full table
    scan ? At glance report ...

    2. Increase the number of db_writer_processes. If the no. or data block waits exceeds a threshold value undo statistics are for rollback segment blocks. If the number of waits is greater than 0 then there is contention for the rollback segment.
    What does all this mean ?

    3. Redo log buffer:
    If too many waits for space in redo log buffer cache occur, then increase the log_buffer parm in init.ora file. Log_buffer must be multiple of operation system blocksize.
    Waits are usually caused by 1. log_buffer being too small 2. Frequent check pointing. 3. Frequent log switching.
    The redo buffer allocation retries should be near to 0.
    redo entries should be less than 1 %.
    redo log space requests indicates active log file is full and server is waiting for space for redo log entries(log switch).
    Is this all true ?

    Can I just update v$parameter for all these ?

    4. What does v$system_event table shows ? What should be the values in there ?

    5. What is enqueue_resources mean ?

    6. What's the query for general database activity statistics ?

    Is there any document that explains all these ?
    Thanks a lot


  2. #2
    Join Date
    Feb 2000
    Washington DC

    Chapter 19,20,21


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