oracle之数据字典屣履造门(三)
number of logical CPUs in the system used by Oracle
0 ksbcpucore number of physical CPU cores in the system used by Oracle
0 ksbcpusocket number of physical CPU sockets in the system used by Oracle
1 ksbcpu_hwm high water mark of number of CPUs used by Oracle
0 ksbcpucore_hwm high water mark of number of CPU cores on system
0 ksbcpusocket_hwm high water mark of number of CPU sockets on system
1 ksbcpu_actual number of available CPUs in the system
1 ksbcpu_dr CPU dynamic reconfiguration supported
33456 kcbnbh number of buffers
25 kcbldq large dirty queue if kcbclw reaches this
40 kcbfsp Max percentage of LRU list foreground can scan for free
KVITVAL KVITTAG KVITDSC
---------- -------------------- --------------------------------------------------------------------------------
2 kcbcln Initial percentage of LRU list to keep clean
800 kcbnbf number buffer objects
0 kcbwst Flag that indicates recovery or db suspension
0 kcteln Error Log Number for thread open
0 kcvgcw SGA: opcode for checkpoint cross-instance call
0 kcvgcw SGA:opcode for pq checkpoint cross-instance call
已选择17行。
SYS@orcl#
kcbldq和kcbfsp是关于dbwr进程进行脏数据写入磁盘的条件。
如下：
SYS@orcl#@getsp.sql
输入 par 的值: db_large_dirty
NAME VALUE PDESC
------------------------------ -------------------- --------------------------------------------------
_db_large_dirty_queue 25 Number of buffers which force dirty queue to be wr
itten
SYS@orcl#
SYS@orcl#@getsp.sql
输入 par 的值: db_block_max_scan
NAME VALUE PDESC
------------------------------ -------------------- --------------------------------------------------
_db_block_max_scan_pct 40 Percentage of buffers to inspect when looking for
free
SYS@orcl#
总结：从这些信息我们可以研究出了lru原理，知道了dbwr进行脏数据写入磁盘的条件。
为了学习，进行尝试修改如下：
SYS@orcl#alter system set "_db_block_max_scan_pct"=50 scope=spfile;
系统已更改。
SYS@orcl#startup force;
ORACLE 例程已经启动。
Total System Global Area 805875712 bytes
Fixed Size 2148720 bytes
Variable Size 562038416 bytes
Database Buffers 234881024 bytes
Redo Buffers 6807552 bytes
数据库已经打开。
SYS@orcl#show parameter _db_block
NAME TYPE VALUE
------------------------------------ ---------------------- ------------------------------
_db_block_max_scan_pct integer 50
SYS@orcl#exit
从
Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options 断开
oracle@oracle:~/test> sqlplus "/as sysdba"
SQL*Plus: Release 11.1.0.6.0 - Production on 星期四 6月 20 21:25:47 2013
Copyright (c) 1982, 2007, Oracle. All rights reserved.
连接到:
Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SYS@orcl#@getsp.sql
输入 par 的值: db_block_max_scan
原值 2: where x.indx=y.indx and x.ksppinm