Oracle 数据字典之x$kvit

x$kvit记录了Oracle使用的cpu数量，后台进程扫描lru列触发增量检查点比例等详细信息，注意该数据字典10g和9i略有不同

引用

SQL> select * from v$version;

BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - Prod
PL/SQL Release 10.2.0.3.0 - Production
CORE    10.2.0.3.0      Production
TNS for Linux: Version 10.2.0.3.0 - Production
NLSRTL Version 10.2.0.3.0 - Production

SQL> desc x$kvit
Name                                      Null?    Type
----------------------------------------- -------- ----------------------------
ADDR                                               RAW(4)
INDX                                               NUMBER
INST_ID                                            NUMBER
KVITVAL                                            NUMBER
KVITTAG                                            VARCHAR2(64)
KVITDSC                                            VARCHAR2(64)

SQL> col KVITTAG for a35
SQL> set linesize 300
SQL> select KVITVAL,KVITTAG,KVITDSC from x$kvit;

   KVITVAL KVITTAG                             KVITDSC
---------- ----------------------------------- ------------------------------------------------------------
        2 ksbcpu                              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
         2 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
         2 ksbcpu_actual                       number of available CPUs in the system
         1 ksbcpu_dr                           CPU dynamic reconfiguration supported
    139930 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
       750 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

17 rows selected.

从红色字体中可以看出，目前Oracle使用的cpu数量为2个，buffer cache中dirty queue脏块比例达到25%，将会触发dbwr写出，同样当后台进程扫描lru列表比例达到40%，还未找到空闲列表，也会触发dbwr写出。通过观察该数据字典，可以形象的看出Oracle内部的一些阀值。