9i and DB_BLOCK_LRU_LATCHES
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Thread: 9i and DB_BLOCK_LRU_LATCHES

  1. #1
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    9i and DB_BLOCK_LRU_LATCHES

    Hi,

    9i DB_BLOCK_LRU_LATCHES ist no longer supported, how does oracle control the number of lru_latches and how can is see/select it?

    Orca

  2. #2
    hi, It is undocumented now.
    21:04:30 SQL> @undocu

    NAME VALUE D S S M A DESCRIPTION
    ------------------------------ ------------------------------ - - - - - ----------------------------------------------------------------
    _db_block_buffers 152022 Y N N N N Number of database blocks cached in memory: hidden parameter
    _db_block_cache_clone FALSE Y N N N N Always clone data blocks on get (for debugging)
    _db_block_cache_num_umap 0 Y N N N N number of unmapped buffers (for tracking swap calls on blocks)
    _db_block_cache_protect FALSE Y N N N N protect database blocks (true only when debugging)
    _db_block_check_for_debug FALSE Y N I N N Check more and dump block before image for debugging
    _db_block_granule_interval 10 Y N I N N number of granules to process
    _db_block_hash_buckets 304049 Y N N N N Number of database block hash buckets
    _db_block_hash_latches 2048 Y N N N N Number of database block hash latches
    _db_block_hi_priority_batch_si 0 Y N N N N Fraction of writes for high priority reasons
    ze


    NAME VALUE D S S M A DESCRIPTION
    ------------------------------ ------------------------------ - - - - - ----------------------------------------------------------------
    _db_block_lru_latches 32 Y N N N N number of lru latches
    _db_block_max_cr_dba 6 Y N N N N Maximum Allowed Number of CR buffers per dba
    _db_block_max_dirty_target 0 Y N I N N Upper bound on modified buffers/recovery reads
    _db_block_max_scan_pct 40 Y N N N N Percentage of buffers to inspect when looking for free
    _db_block_med_priority_batch_s 0 Y N N N N Fraction of writes for medium priority reasons
    ize

    _db_block_numa 1 Y N N N N Number of NUMA nodes
    _db_block_prefetch_quota 10 Y N I N N Prefetch quota as a percent of cache size
    _db_block_trace_protect FALSE Y N I N N trace buffer protect calls
    www.cnoug.org

  3. #3
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    Good,
    can you post me your script?
    Thank you very much
    Orca

  4. #4
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    Re: 9i and DB_BLOCK_LRU_LATCHES

    Originally posted by Orca777
    9i DB_BLOCK_LRU_LATCHES ... how can is see/select it?
    Code:
    select count(*) from v$latch_children
    where name = 'cache buffers lru chain';
    From metalink...
    In Oracle9i, the parameter DB_BLOCK_LRU_LATCHES is obsolete (listed in the desupported/depreciated init.ora parameter section of the Oracle 9i New Features guide). This is now a hidden parameter that defaults based on the value of cpu_count or db_writer_processes if explictly set, as well as several other factors(which includes the max # of caches ). A setting of db_writer_processes = 4 seems to adjust the hidden parameter to 32. Since this is now a hidden parameter, I would keep in mind that the formula (and therefore the value)is subject to change with subsequent versions.
    HTH.

  5. #5
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    Thanks a lot!!
    Orca


    PS.: what is the select for internal paramts ( some k$-Table ??)

  6. #6
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    Yet another note from metalink...


    You cannot set DB_BLOCK_LRU_LATCHES in 9i--it is computed automatically. The number of LRU latches in each buffer pool for each block size will be equal to the half the number of CPUs.
    HTH.

  7. #7
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    Script for finding undocumented parameters

    Code:
    SELECT   a.ksppinm parameter
            ,a.ksppdesc description
            ,b.ksppstvl session_value
            ,c.ksppstvl instance_value
        FROM x$ksppi a
            ,x$ksppcv b
            ,x$ksppsv c
       WHERE a.indx = b.indx AND a.indx = c.indx AND SUBSTR (a.ksppinm
                                                            ,1
                                                            ,1
                                                            ) = '_'
    ORDER BY a.ksppinm
    /
    HTH
    Amar
    "There is a difference between knowing the path and walking the path."

    Amar's Blog  Get Firefox!

  8. #8
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  9. #9
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    just use v$fixed_view_definition

  10. #10
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    This is extraordinary!!
    I post a topic and
    you answered it all perfectly in < 5 Minutes!!

    :-)))))))))))))))))

    Orca

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