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Oracle's x$ Tables

原创 Oracle 作者:qiuyb 时间:2006-03-22 16:14:23 0 删除 编辑
常用的Oracle x$ Tables,本文章源自:[@more@]


Information on buffer headers.
Contains a record (the buffer header) for each block in the .
This select statement lists how many blocks are Available, Free and Being Used.
select count(*), State from (
    select  (state, 
       0, 'Free',
       1, decode (lrba_seq,
          0, 'Available',
             'Being Used'),
       3, 'Being Used',
          state) State
     from x$bh )
    group by state
The meaning of state:
0FREEno valid block image
1XCURa current mode block, exclusive to this instance
2SCURa current mode block, shared with other instances
3CR a consistent read (stale) block image
4READbuffer is reserved for a block being read from disk
5MRECa block in media recovery mode
6IRECa block in instance (crash) recovery mode
The meaning of tch: tch is the touch count. A high touch count indicates that the buffer is used often. Therefore, it will probably be at the head of the MRU list. See also .
The meaning of tim: touch time.
class represents a value designated for the use of the block.
set_ds maps to addr on x$kcbwds.
le_addr can be outer joined on x$le.le_addr.
flag is a bit array.
Bitif set
0Block is dirty
4temporary block
9 or 10ping
524288 (=0x80000)Block was read in a See


Buffer pool descriptor, the base table for .
How is the buffer cache split between the , the and the buffer pool.


Set descriptor, see also x$kcbwbpd
The column id can be joined with .
The column bbwait corresponds to the wait event.
Information on working set buffers
addr can be joined with x$bh.set_ds.
set_id will be between lo_setid and hi_setid in for the relevant buffer pool.


Controlfile logfile entry. Use
select max(lebsz) from x$kccle
to find out the size of a log block. The log block size is the unit for the following init params: , , and .


Checkpoint Progress:
The column cpodr_bno displays the current redo block number. Multiplied with the OS Block Size (usually 512), it returns the amount of bytes of redo currently written to the redo logs. Hence, this number is reset at each .
k$kcccp can (together with x$kccle) be used to monitor the progress of the writing of . The following query does this.
  le.leseq                        "Current log sequence No",
  100*cp.cpodr_bno/le.lesiz       "Percent Full",
  cp.cpodr_bno                    "Current Block No",
  le.lesiz                        "Size of Log in Blocks"
  x$kcccp cp,
  x$kccle le
  LE.leseq =CP.cpodr_seq
  and bitand(le.leflg,24)=8;
bitand(le.leflg,24)=8 makes sure we get the current log group
How much Redo is written by Oracle uses a variation of this SQL statement to track how much redo is written by different DML Statements.


This table lists all held and requested library object locks for all sessions. It is more complete than .
The column kglnaobj displays the first 80 characters of the name of the object.
  kglnaobj, kgllkreq
  x$kgllk x join v$session s on 
    s.saddr = x.kgllkses;
kgllkreq = 0 means, the lock is held, while kgllkreq > 0 means that the lock is requested.
1、KGLLKHDL:对应于v$session_wait的p1raw列,表明library cache lock的锁地址。也对应于x$kglob的kglhdadr这一列。
4、KGLNAOBJ:包含了在librarky cache中的对象上执行命令的语句的前80个字符。
5、KGLLKMOD:代表的锁"占用"模式,0-> 'None', 1->'Null', 2-> 'Share', 3-> 'Exclusive',其它值->'Unknown'
6、KGLLKREP:代表"请求"模式,0-> 'None', 1->'Null', 2-> 'Share', 3-> 'Exclusive',其它值->'Unknown',另一个角度说明0->lock的占有者,其它->锁的请求者。


This table has an entry for each column of the x$tables and can be joined with x$kqfta.
The column kqfcosiz indicates the size (in bytes?) of the columns.
  t.kqftanam "Table Name",
  c.kqfconam "Column Name",
  c.kqfcosiz "Column Size"
  x$kqfta t,
  x$kqfco c
  t.indx = c.kqfcotab


It seems that all x$table names can be retrieved with the following query.
select kqftanam from x$kqfta;
This table can be joined with x$kqfco which contains the columns for the tables:
  t.kqftanam "Table Name",
  c.kqfconam "Column Name"
  x$kqfta t,
  x$kqfco c
  t.indx = c.kqfcotab


Memory least recently used
Whenever a select is performed on x$ksmlru, its content is reset!
This table show which memory allocations in the caused the throw out of the biggest memory chunks since it was last queried.


This 'table' seems to allow to address (that is read (write????)) every byte in the . Since the size of the SGA equals the size of select sum(value) from v$sga, the following query must return 0 (at least on a four byte architecture. Don't know about 8 bytes.)
  (select sum(value)  from   ) -
  (select 4*count(*) from x$ksmmem) "Must be Zero!"


Contains the value kspftctxvl for each parameter found in x$ksppi. Determine if this value is the default value with the column kspftctxdf.


This table contains a record for all documented and undocumented (starting with an underscore) parameters. select ksppinm from x$ksppi to show the names of all parameters. Join indx+1 with x$ksppcv2.kspftctxpn.


Enqueue management statistics by type.
ksqstwat: The number of wait for the enqueue statistics class.
ksqstwtim: Cumulated waiting time. This column is selected when
v$enqueue_stat.cum_wait_time is selected.
The types of classes are:
BLBuffer Cache Management
CF Transaction
CICross-instance call invocation
CUBind Enqueue
DLDirect Loader index creation
DMDatabase mount
DRDistributed Recovery
DXDistributed TX
FBacquired when formatting a range of bitmap blocks far ASSM segments. id1=ts#, id2=relative dba
FSFile Set
INInstance number
IRInstance Recovery
ISInstance State
IVLibrary cache invalidation
JDSomething to do with
JQJob queue
KKRedo log kick
LA..LP lock
MDenqueue for Change data capture materialized view log (gotten internally for DDL on a snapshot log) id1=object# of the snapshot log.
MRMedia recovery
NA..NZ pin
PFPassword file
PIParallel slaves
PRProcess startup
PSParallel slave synchronization
SQ number enqueue
SRSynchronized replication
SSSort segment
STSpace management transaction
SVSequence number value
SWSuspend writes enqueue gotten when someone issues
TATransaction recovery
ULUser defined lock
UNUser name
USUndo segment, serialization
WLRedo log being written
XAInstance attribute lock
XIInstance registration lock
XRAcquired for


Contains a record for all .


The transaction table.


Lists save undo for each tablespace: The column kttvstnm is the name of the that has saved undo. The column is null otherwise.


Kernel transaction, undo transaction entry


Has (among others) a row containing the db block size:
 select kvisval from x$kvis where kvistag = 'kcbbkl'


Lock element: contains an entry for each PCM lock held for the buffer cache. x$le can be left outer joined to x$bh on le_addr.


A perlscript to find x$ tables

#!/usr/bin/perl -w

use strict;

open O, ("/appl/oracle/product/");
open F, (">x");

my $l;
my $p = ' ' x 40;
my %x;

while (read (O,$l,10000)) {
  $l = $p.$l;

  foreach ($l =~ /(x$w{3,})/g) {

  $p = substr ($l,-40);

foreach (sort keys %x) {
  print F "$_n";

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