Patent ID: 7991775
Filing Date: 2011-08-02
Classification: G06F,Y10S

Abstract:
1. A computer-implemented method, comprising: a multi-node database server computing a snapshot query associated with a snapshot time, wherein said multi-node database server manages access to a database comprising database data blocks; said multi-node database server generating a global checkpoint system change number, wherein any data block of said database data blocks that is associated with a system change number that is less than said global checkpoint system change number is stored persistently in said database; wherein computing said snapshot query comprises: said multi-node database server determining whether said snapshot time is less than said global checkpoint system change number; when said snapshot time is less than said global checkpoint system change number, said multi-node database server accessing data blocks of said database data blocks without obtaining a global lock for any of said data blocks of said database data blocks; and when said snapshot time is greater than said global checkpoint system change number, said multi-node database server accessing data blocks of said database data blocks, and obtaining a global lock on said data blocks of said database data blocks to access any of said data block of said database data blocks.