Sybase, Inc.

Joe Francis

Satya Ramachandran

Fei Zhou

Srikanth Sampath

Mei-Lin Linda Lin

Gangavara Prasad Varakur

A distributed database system providing data and space management methodology. In one embodiment a system for allocating resources amongst a plurality of database servers sharing resources comprises: an input module for receiving user input for allocating resources shared amongst a plurality of database servers and establishing thresholds for utilization of resources at each database server; a monitoring module at each database server for monitoring local resource utilization at each database server and sending a request for balancing resources to a second database server when local resource utilization reaches an established threshold at a first database server; and a load balancing module for receiving the request for balancing resources and determining whether to adjust resources allocated to the first database server and the second database server in response to the request.

Distributed database system providing data and space management methodology

A distributed database system providing data and space management methodology. In a distributed database system having an allocation page for tracking allocation and deallocation of data pages including a deallocation bit for tracking data page deallocation, a method for determining when to clear the deallocation bit during recovery comprises: during runtime operation, generating log records recording allocation and deallocation of data pages, setting the deallocation bit during deallocation of a data page by a transaction, and clearing the deallocation bit after the transaction has committed; during recovery following a failure, identifying a particular log record corresponding to the deallocation bit set during deallocation of a given data page; determining whether the deallocation of the given data page recorded in the particular log record committed prior to the failure; and if the deallocation of the given data page committed prior to the failure, clearing the deallocation bit.

A distributed database system providing data and space management methodology. In a distributed system consisting a plurality of servers sharing access to data pages, a method for setting a timestamp indicating when modifications to data pages are made in a non-regressing fashion includes steps of: maintaining a local sequence at each server and an allocation page timestamp on an allocation page; upon allocation of a data page, applying a timestamp to the data page which is greater than the allocation page timestamp; upon modification of a given data page at a particular server, setting the timestamp on the given data page to the greater of the local sequence at the particular server and an existing timestamp already on the given data page; and when data pages are deallocated, adjusting the allocation page timestamp to a value greater than the timestamp value on any deallocated data page.

A distributed database system providing data and space management methodology is described. In one embodiment, for example, a method is described for detection of deadlocks in a distributed database system comprising a plurality of servers sharing access to data, the method comprises steps of: in response to a task at a first server waiting to obtain a lock regulating access to data, sending a search request including lock information to a second server holding the lock; at the second server, examining dependencies of the task holding the lock based on the lock information received with the search request and local lock information; if the task holding the lock is waiting to obtain a lock held by an additional server, forwarding the search request and local lock information to the additional server; repeating the examining and forwarding steps until all dependencies are examined; and responding to the search request indicating whether a deadlock was detected and providing lock information found.

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Fremont, CA, United States of America

Joe Francis