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Thread: x$bh

  1. #1
    Join Date
    Jul 2001
    Posts
    108
    Hello,

    Is there any corresponding view or synonym availbale for sys.x$bh?

    Thanks
    Nikee

  2. #2
    Join Date
    Mar 2001
    Posts
    314
    There does not seem to be any view with a 1-1 correspondence with x$bh. But gv$bh comes closest to it.

    That's as far as my knowledge goes. I may be wrong

    -amar

  3. #3
    Join Date
    Dec 2000
    Location
    Ljubljana, Slovenia
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    4,439
    No, amar, you are not wrong.

    V$BH (or GV$BH for that matter) is the "outer representation" of X$BH. And they do have one-to-one relationship, at least in the meaning that each row from V$BH coresponds to exactly one row in X$BH. Some of the collumns from X$BH are ommited from V$BH, some are slightly transformed, and some of the columns in V$BH are obtained from outer-joned X$LE, but basicaly there is 1:1 relationship between X$BH and V$BH.
    Jurij Modic
    ASCII a stupid question, get a stupid ANSI
    24 hours in a day .... 24 beer in a case .... coincidence?

  4. #4
    Join Date
    Jun 2001
    Location
    Helsinki. Finland
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    3,938
    The difference between GV$BH and V$BH is that the global buffer header view shows the buffer header information for all instances. That is, if you run a multi-instance DB, then GV$BH might be very of great help in order to find the block numbers of blocks experiencing a lot of FORCE_READS and FORCED_WRITES. Then you can find the rows in those blocks. Do you know how (there is slight difference in 7 and 8).

    V$BH returns status number and the number of X-to-NULL lock conversions, forced reads and writes but no info on the DB objects realted to that block. But if this is of interest, join V$BH with OBJ$.

    Several view are based on V$BH, V$CACHE, V$PING. But if you do not run OPS you are really not interested in them.


  5. #5
    Join Date
    Dec 2000
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    Ljubljana, Slovenia
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    4,439
    Originally posted by julian
    Several view are based on V$BH, V$CACHE, V$PING. But if you do not run OPS you are really not interested in them.
    Well, V$BH can definitely be of great interest even on non-OPS systems if you want to know which blocks of which objects are currently in your buffer cache and what's happening to them....
    Jurij Modic
    ASCII a stupid question, get a stupid ANSI
    24 hours in a day .... 24 beer in a case .... coincidence?

  6. #6
    Join Date
    Jun 2001
    Location
    Helsinki. Finland
    Posts
    3,938

    Well, V$BH can definitely be of great interest even on non-OPS systems if you want to know which blocks of which objects are currently in your buffer cache and what's happening to them....
    Right. However, it is not the first (synonym of a) view you would work with in a single env. How often do you query the buffer header view? Not every day I guess.

    I use it almost every day (force reads and writes).


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