Database system configured for automatic failover with no data loss
First Claim
1. An automatic failover configuration comprising:
- participants including a primary database system that processes transactions and produces redo data therefor;
a standby database system that receives the redo data via a communications link;
an observer; and
system state specifiers which prevent the automatic failover from resulting in divergence of the database systems while permitting the primary database system to continue to process redo data when both the observer and the standby database system are absent as long as the observer and the standby database system became absent sequentially.
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Accused Products
Abstract
Techniques used in an automatic failover configuration having a primary database system, a standby database system, and an observer for preventing divergence among the primary and standby database systems while increasing the availability of the primary database system. In the automatic failover configuration, the primary database system remains available even in the absence of both the standby and the observer as long as the standby and the observer become absent sequentially. The failover configuration further permits automatic failover only when the observer is present and the standby and the primary are synchronized and inhibits state changes during failover. The database systems and the observer have copies of failover configuration state and the techniques include techniques for propagating the most recent version of the state among the databases and the observer and techniques for using carefully-ordered writes to ensure that state changes are propagated in a fashion which prevents divergence.
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Citations
25 Claims
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1. An automatic failover configuration comprising:
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participants including a primary database system that processes transactions and produces redo data therefor;
a standby database system that receives the redo data via a communications link;
an observer; and
system state specifiers which prevent the automatic failover from resulting in divergence of the database systems while permitting the primary database system to continue to process redo data when both the observer and the standby database system are absent as long as the observer and the standby database system became absent sequentially. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. An automatic failover configuration comprising:
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participants including a primary database system that processes transactions and produces redo data therefor;
a standby database system that receives the redo data via a communications link;
an observer; and
system state specifiers which prevent the automatic failover from resulting in divergence of the database systems by preventing the automatic failover from occurring if no failover condition has occurred or if the standby database system is suspended or not in synchrony with the primary database system or the observer is seen as absent and which continue to prevent a further automatic failover until the automatic failover is complete. - View Dependent Claims (24, 25)
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Specification