Identifying database request sources in multi-database systems

摘要

Recovering from a failure of a soon-to-fail database system among a plurality of database systems in a multi-database system in processing a request submitted to the multi-database system through a multi-database system session is accomplished. A query band is created for the request. The query band is defined to be an identifier that uniquely identifies the session and the request among the plurality of sessions and plurality of requests being processed by the multi-database system at the time that the request was submitted. The query band is attached to a transaction issued by the multi-database system to the soon-to-fail database system to execute the query. The status concerning execution of the transaction is reported by the soon-to-fail database system. The status includes the query band. The status is logged. The failure of the soon-to-fail database system is detected. The state of the soon-to-fail database system is reconstructed from the logged status as the state related to the processing of the transaction using the query band. The reconstructed state is used to continue processing of the transaction by an alternative database system. The alternative database system is one of the plurality of database systems in the multi-database system. The request is processed to produce a result and the result is stored.