Patent ID: 7822727
Filing Date: 2010-10-26
Classification: G06F

Abstract:
1. A method, comprising: creating a shadow cache configured to hold at least one modified block that has been physically redone and undone or that has been logically undone; collecting an active transaction list of all active transactions when a read-only transaction starts; determining a first log sequence number and a second log sequence number associated with the active transaction list, the first log sequence number and the second log sequence number specifying a set of transactions capable of being physically redone and undone or logically undone, wherein the second log sequence number is greater than the first log sequence number; loading a modified block into a read-only cache view, the modified block including a log sequence number; comparing the log sequence number to both the first log sequence number and the second log sequence number; performing physical redo operations or physical undo operations based upon the comparing as the another modified block is loaded into the read-only cache view, wherein the physical redo operations or the physical undo operations are not performed on the modified block when the log sequence number is less than the first log sequence number, and the physical redo operations are performed on the modified block when the log sequence number is greater than the first log sequence number and less than the second log sequence number, and the physical undo operations are performed on the modified block when the log sequence number is greater than the second log sequence number; processing the active transaction list to physically undo an incomplete action and to logically undo an active transaction to generate transactional consistency in the read-only cache view; creating one or more other modified blocks to generate the transactional consistency in the read-only cache view; and determining the one or more other modified blocks being stored in the shadow cache and not an original database when a shared cache overflows.