了避免DBWR不必要的喚醒及過于活躍,從Oracle10g開始,Oracle對DBWR的SCAN間隔進(jìn)行了調(diào)整. 在內(nèi)部由一個隱含參數(shù):_dbwr_scan_interval 控制.Oracle9i中這個參數(shù)缺省值為10 s: SQL> select * from v$version; 2; /BANNER----------------------------------------------------------------Oracle9i Enterprise Edition Release 9.2.0.4.0 - 64bit ProdUCtionPL/SQL Release 9.2.0.4.0 - ProductionCORE;9.2.0.3.0;;;;ProductionTNS for Solaris: Version 9.2.0.4.0 - ProductionNLSRTL Version 9.2.0.4.0 - ProductionSQL> col ksppinm for a20SQL> col ksppdesc for a40SQL> col ksppstvl for a10SQL> select; 2;ksppinm,ksppdesc,ksppstvl; 3; from; 4;sys.x$ksppi x,; 5;sys.x$ksppcv y; 6; where; 7;x.inst_id = userenv('Instance') and; 8;y.inst_id = userenv('Instance') and; 9;x.indx = y.indx and 10;x.ksppinm like '%_dbwr_scan%' 11; /KSPPINM;;;KSPPDESC KSPPSTVL-------------------- ---------------------------------------- ----------_dbwr_scan_interval; dbwriter scan interval10 從Oracle10g開始,此缺省值被調(diào)這個為300 s:SQL> select * from v$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 - ProductionSQL> 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 interval300 ;在Oracle10gR2中,這個參數(shù)未作進(jìn)一步調(diào)整,缺省值仍然為300:SQL> select * from v$version; 2; /BANNER----------------------------------------------------------------Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - ProdPL/SQL Release 10.2.0.1.0 - ProductionCORE;10.2.0.1.0;;;ProductionTNS for Linux: Version 10.2.0.1.0 - ProductionNLSRTL Version 10.2.0.1.0 - ProductionSQL> col ksppinm for a20SQL> col ksppdesc for a40SQL> col ksppstvl for a10SQL> select; 2;ksppinm,ksppdesc,ksppstvl; 3; from; 4;sys.x$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 interval300 以上內(nèi)容,僅供參考.