了避免DBWR不必要的唤醒及过于活跃,从Oracle10g开始,Oracle对DBWR的SCAN间隔进行了调整.
在内部由一个隐含参数:_dbwr_scan_interval 控制.
Oracle9i中这个参数缺省值为10 s:
SQL> select * from v$version 2 /
BANNER----------------------------------------------------------------Oracle9i Enterprise Edition Release 9.2.0.4.0 - 64bit ProductionPL/SQL Release 9.2.0.4.0 - ProductionCORE 9.2.0.3.0 ProductionTNS for Solaris: Version 9.2.0.4.0 - ProductionNLSRTL Version 9.2.0.4.0 - Production
SQL> col ksppinm for a20SQL> col ksppdesc for a40SQL> col ksppstvl for a10SQL> select 2 ksppinm,ksppdesc,ksppstvl 3 from 4 sys.x$ksppi x, 5 sys.x$ksppcv y 6 where 7 x.inst_id = userenv('Instance') and 8 y.inst_id = userenv('Instance') and 9 x.indx = y.indx and 10 x.ksppinm like '%_dbwr_scan%' 11 /
KSPPINM KSPPDESC KSPPSTVL-------------------- ---------------------------------------- ----------_dbwr_scan_interval dbwriter scan interval 10
从Oracle10g开始,此缺省值被调这个为300 s:
SQL> select * from v$version 2 /
BANNER----------------------------------------------------------------Oracle Database 10g Enterprise Edition Release 10.1.0.3.0 - 64biPL/SQL Release 10.1.0.3.0 - ProductionCORE 10.1.0.3.0 ProductionTNS for Solaris: Version 10.1.0.3.0 - ProductionNLSRTL Version 10.1.0.3.0 - Production
SQL> col ksppinm for a20SQL> col ksppdesc for a40SQL> col ksppstvl for a10SQL> select 2 ksppinm,ksppdesc,ksppstvl 3 from 4 sys.x$ksppi x, 5 sys.x$ksppcv y 6 where 7 x.inst_id = userenv('Instance') and 8 y.inst_id = userenv('Instance') and 9 x.indx = y.indx and 10 x.ksppinm like '%_dbwr_scan%' 11 /
KSPPINM KSPPDESC KSPPSTVL-------------------- ---------------------------------------- ----------_dbwr_scan_interval dbwriter scan interval 300
在Oracle10gR2中,这个参数未作进一步调整,缺省值仍然为300:
SQL> select * from v$version 2 /
BANNER----------------------------------------------------------------Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - ProdPL/SQL Release 10.2.0.1.0 - ProductionCORE 10.2.0.1.0 ProductionTNS for Linux: Version 10.2.0.1.0 - ProductionNLSRTL Version 10.2.0.1.0 - Production
SQL> col ksppinm for a20SQL> col ksppdesc for a40SQL> col ksppstvl for a10SQL> select 2 ksppinm,ksppdesc,ksppstvl 3 from 4 sys.x$ksppi x, 5 sys.x$ksppcv y 6 where 7 x.inst_id = userenv('Instance') and 8 y.inst_id = userenv('Instance') and 9 x.indx = y.indx and 10 x.ksppinm like '%_dbwr_scan%' 11 /
KSPPINM KSPPDESC KSPPSTVL-------------------- ---------------------------------------- ----------_dbwr_scan_interval dbwriter scan interval 300
以上内容,仅供参考.