DBWR enhancements In Oracle10g

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为了避免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 Production
PL/SQL Release 9.2.0.4.0 - Production
CORE    9.2.0.3.0       Production
TNS for Solaris: Version 9.2.0.4.0 - Production
NLSRTL Version 9.2.0.4.0 - Production

SQL> col ksppinm for a20
SQL> col ksppdesc for a40
SQL> col ksppstvl for a10
SQL> 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 - 64bi
PL/SQL Release 10.1.0.3.0 - Production
CORE    10.1.0.3.0      Production
TNS for Solaris: Version 10.1.0.3.0 - Production
NLSRTL Version 10.1.0.3.0 - Production

SQL> col ksppinm for a20
SQL> col ksppdesc for a40
SQL> col ksppstvl for a10
SQL> 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 - Prod
PL/SQL Release 10.2.0.1.0 - Production
CORE    10.2.0.1.0      Production
TNS for Linux: Version 10.2.0.1.0 - Production
NLSRTL Version 10.2.0.1.0 - Production

SQL> col ksppinm for a20
SQL> col ksppdesc for a40
SQL> col ksppstvl for a10
SQL> 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.

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