關于oracle db 11gR2版本上的_external_scn_rejection_threshold_hours參數和scn headroom更新檔問題

關于oracle db 11gR2版本上的_external_scn_rejection_threshold_hours參數和scn headroom更新檔問題

第一點：

In addition to the above result the script output may advise to set the hidden parameter "_external_scn_rejection_threshold_hours" on some Oracle versions. The following text gives more information about setting this parameter:

Set _external_scn_rejection_threshold_hours=24 after apply

Oracle recommends setting this parameter to the value 24 in 10g and 11.1 releases - it does not need to be set in 11.2 or later releases. The parameter is static and so must be set in the init.ora or spfile used to start the instance. 

eg:

In init.ora: 

  # Set threshold on dd/mon/yyyy - See MOS Document 1393363.1

  _external_scn_rejection_threshold_hours = 24 

In the spfile: 

  alter system set "_external_scn_rejection_threshold_hours" = 24 

   comment='Set threshold on dd/mon/yyyy - See MOS Document 1393363.1' 

   scope=spfile ;

從以上可以看出，在 11.2及其更高的版本上，是無需設定_external_scn_rejection_threshold_hours參數的。

實際上，在11.2.0.4的db軟體中，該參數已經出現在隐含參數中了。

第二點：

Please note that there are no SCN hardening fixes for the following versions. The recommendation for these versions is to upgrade to a newer release:
  All versions up to and including 9.2.0.7
  Versions 10.1.0.2 to 10.1.0.4 inclusive
  Versions 10.2.0.1 and 10.2.0.2
  Version 11.1.0.6
  Version 11.2.0.1      

從這句話可以看出：以上版本的oracle資料庫軟體沒有修複scn headroom 的更新檔。請更新到更新的版本。這一招夠狠的。

Versions 11.2.0.4 and 12.1.0.1 onwards already include the main SCN fixes but the "scnhealthcheck" script described above can still be used on those releases to check the current headroom.