The database server interprets either of the following conditions as an HDR failure:
During normal HDR operation, a database server expects confirmation of communication from the other database server in the pair. Each database server in the pair has an ONCONFIG parameter, DRTIMEOUT, that specifies a number of seconds. If confirmation from the other database server in a pair does not return within the number of seconds that DRTIMEOUT specifies, the database server assumes that an HDR failure has occurred.
The database servers ping each other regardless of whether the primary database server sends any records to the secondary database server. If one database server of a primary-secondary pair does not respond to four sequential ping attempts, the other database server assumes that an HDR failure has occurred.
Each database server in the pair sends a ping to the other database server in the pair when the number of seconds specified by the DRTIMEOUT parameter on that database server has passed.