強制歸檔引數ARCHIVE_LAG_TARGET

          在Standby 環境中，為了減少出現故障時資料損失，我們可以設定ARCHIVE_LAG_TARGET引數，強制進行日誌切換。ARCHIVE_LAG_TARGET引數可以設定一個時間，透過時間限制，指定資料庫強制進行Log Switch，進行歸檔。 這個引數的預設值是0，即為不啟用該引數。該引數合理的取值範圍在60 ~ 7200之間。 通常大於7200和小於1800不被推薦，低於30分鐘的切換時間可能導致效能問題。 

 

Property	Description
Parameter type	Integer
Default value	0 (disabled)
Modifiable	ALTER SYSTEM
Range of values	0 or any integer in [60, 7200]
Basic	No
Real Application Clusters	Multiple instances should use the same value.

ARCHIVE_LAG_TARGET limits the amount of data that can be lost and effectively increases the availability of the standby database by forcing a log switch after the specified amount of time elapses.

A 0 value disables the time-based thread advance feature; otherwise, the value represents the number of seconds. Values larger than 7200 seconds are not of much use in maintaining a reasonable lag in the standby database. The typical, or recommended value is 1800 (30 minutes).    Extremely low values can result in frequent log switches, which could degrade performance;    such values can also make the archiver process too busy to archive the continuously generated logs.