Abstract: A system uses a hybrid key-value storage engine that uses log-structured merge tree and a segmented log-structured object store. The system performs garbage collection of stale document versions avoiding index lookup during log segment compaction. The system separates index and document data to minimize write amplification. The system maintains a delete list using a log-structured merge-tree to store stale document sequence numbers and corresponding sizes per log segment. For each log segment from the plurality of log segments, the system determines a measure of fragmentation of the log segment based on sizes of deleted documents of the log segment from the second log-structured merge-tree. If the fragmentation exceeds a threshold, the system initiates a compaction operation for the log segment.

Abstract: A system uses a hybrid key-value storage engine that uses log-structured merge tree and a segmented log-structured object store. The system performs garbage collection of stale document versions avoiding index lookup during log segment compaction. The system separates index and document data to minimize write amplification. The system maintains a delete list using a log-structured merge-tree to store stale document sequence numbers and corresponding sizes per log segment. For each log segment from the plurality of log segments, the system determines a measure of fragmentation of the log segment based on sizes of deleted documents of the log segment from the second log-structured merge-tree. If the fragmentation exceeds a threshold, the system initiates a compaction operation for the log segment.

Abstract: A system for improved data sharing within a cluster of nodes having a database management system. The system defines a virtual replicated table as being useable in a hybrid of a shared-cache and shared-nothing architecture. The virtual replicated table is a physically single table sharable among a plurality of cluster nodes for data read operations and not sharable with other cluster nodes for data modification operations. Default owner node is assigned for each virtual replicated table to ensure the page validity and provide requested pages to the requesting node.

Abstract: A system for limiting the amount of time for a database server to perform a crash recovery process. A maximum recovery time for the database server to perform the crash recovery process is specified. An estimated recovery time for the crash recovery process that is less than the maximum recovery time is calculated, based on at least one of a deterministic analysis of cost accumulation during prior instances of the crash recovery process or an empirical analysis of cost accumulation during regular transaction processing in the database server. The crash recovery process is then conformed to the estimated recovery time.

Abstract: Embodiments of the invention generally relate to data processing systems and more particularly to high availability data processing systems. A primary server may share a storage device with one or more clone systems. Each clone generally replicates the state of the primary server, but relies on the same disk-based storage as the primary server. Thus, the clone systems may provide a shadow of the primary server, ready to take over should the primary server fail. The clone systems may access a log file that includes entries reflecting the actions performed by the primary system. The primary server may flush entries from a log buffer maintained on the primary server to a log file stored on the shared disk-based storage. The primary server may also send a log sequence number to the clone systems, and the clone systems periodically transmit a log sequence number back to the primary server indicating how far through the log file a clone system has progressed.

Abstract: A partial-blocking consistency point system identifies transaction updates with a consistency point ID associated with a consistency point sequence number, records consistency point data that identify a location of the partial-blocking consistency point, flushes to a non-volatile storage the transaction updates identified with the consistency point sequence number without blocking transaction activity, and hardens to the non-volatile storage the recorded partial-blocking consistency point so that data associated with the recorded partial-blocking consistency point can be recovered. The consistency point sequence number is incremented each time the partial-blocking consistency point is recorded to uniquely identify the partial-blocking consistency point and transaction updates associated with the partial-blocking consistency point. The transaction updates identified with the consistency point sequence number are processed to improve efficiency of the flushing of the transaction updates.

Abstract: The present invention expounds upon the ANSI “read committed” isolation level by allowing readers to read committed data without waiting for a concurrent writer to the data to finish. The method returns a last committed version of the data as it existed prior to changes made by the concurrent writer. Only two versions of any data record are required to be stored in the record data store, the last committed version and the current version. The last committed version may be generated from an undo log record. Locating the appropriate undo log record may be accomplished by storing a log sequence number in a lock data structure associated with the requested data record. A transaction flag may also stored in the lock data structure to facilitate generating the last committed version. The method may also utilize one or more locks to detect a concurrent writer to the requested data.

Abstract: A system for improved data sharing within a cluster of nodes having a database management system. The system defines a virtual replicated table as being useable in a hybrid of a shared-cache and shared-nothing architecture. The virtual replicated table is a physically single table sharable among a plurality of cluster nodes for data read operations and not sharable with other cluster nodes for data modification operations. Default owner node is assigned for each virtual replicated table to ensure the page validity and provide requested pages to the requesting node.

Abstract: Embodiments of the invention relate to data processing systems and more specifically to high availability data processing systems comprising a primary server and a secondary server. The secondary server may receive an update request from a client. The secondary server may perform one or more preliminary operations required for processing of the update request. The secondary server may then redirect a partially processed update operation to the primary server for execution. Therefore, greater load balancing is achieved between the servers and more efficient utilization of secondary server resources is achieved.

Abstract: A method for improved data sharing within a cluster of nodes having a database management system. The method defines a virtual replicated table as being useable in a hybrid of a shared-cache and shared-nothing architecture. The virtual replicated table is a physically single table sharable among a plurality of cluster nodes for data read operations and not sharable with other cluster nodes for data modification operations. Default owner node is assigned for each virtual replicated table to ensure the page validity and provide requested pages to the requesting node.

Abstract: Embodiments of the invention generally relate to data processing systems and more particularly to high availability data processing systems. A primary server may share a storage device with one or more clone systems. Each clone generally replicates the state of the primary server, but relies on the same disk-based storage as the primary server. Thus, the clone systems may provide a shadow of the primary server, ready to take over should the primary server fail. The clone systems may access a log file that includes entries reflecting the actions performed by the primary system. The primary server may flush entries from a log buffer maintained on the primary server to a log file stored on the shared disk-based storage. The primary server may also send a log sequence number to the clone systems, and the clone systems periodically transmit a log sequence number back to the primary server indicating how far through the log file a clone system has progressed.

Abstract: A system for data base management using memory devices holding a database containing tables of data occupying extents. A database engine reviews each query to determine an extents list of extents containing the data needed by that said query. A query monitor then re-orders the extents lists so that extents are retrieved and stored in a buffer cache for more efficient use when executing the queries. The database engine retrieves needed extents from the memory devices, as ordered in the extents lists, and stores those extents in the buffer cache. The database engine then executes one or more queries on the data in the extents in the buffer cache to determine respective results.

Abstract: The present invention expounds upon the ANSI “read committed” isolation level by allowing readers to read committed data without waiting for a concurrent writer to the data to finish. The method returns a last committed version of the data as it existed prior to changes made by the concurrent writer. Only two versions of any data record are required to be stored in the record data store, the last committed version and the current version. The last committed version may be generated from an undo log record. Locating the appropriate undo log record may be accomplished by storing a log sequence number in a lock data structure associated with the requested data record. A transaction flag may also stored in the lock data structure to facilitate generating the last committed version. The method may also utilize one or more locks to detect a concurrent writer to the requested data.

Abstract: A system for data base management using memory devices holding a database containing tables of data occupying extents. A database engine reviews each query to determine an extents list of extents containing the data needed by that said query. A query monitor then re-orders the extents lists so that extents are retreived and stored in a buffer cache for more efficient use when executing the queries. The database engine retreives needed extents from the memory devices, as ordered in the extents lists, and stores those extents in the buffer cache. The database engine then executes one or more queries on the data in the extents in the buffer cache to determine respective results.

Abstract: A method of searching for information within a database that includes: identifying a set of leading index key columns, from among a plurality of index key columns, that has a limited number of unique values; utilizing the identified set of leading index key columns to perform an index scan in order to retrieve each unique value from the set of leading index key columns; and utilizing each of the retrieved unique values from the set of leading index key columns to perform an index lead key self-join operation, such that predicates on the non-leading index key columns are utilized to position an index scan operation.

Abstract: A partial-blocking consistency point system identifies transaction updates with a consistency point ID associated with a consistency point sequence number, records consistency point data that identify a location of the partial-blocking consistency point, flushes to a non-volatile storage the transaction updates identified with the consistency point sequence number without blocking transaction activity, and hardens to the non-volatile storage the recorded partial-blocking consistency point so that data associated with the recorded partial-blocking consistency point can be recovered. The consistency point sequence number is incremented each time the partial-blocking consistency point is recorded to uniquely identify the partial-blocking consistency point and transaction updates associated with the partial-blocking consistency point. The transaction updates identified with the consistency point sequence number are processed to improve efficiency of the flushing of the transaction updates.

Abstract: A method, apparatus and article of manufacture, implementing the method, accesses rows in a range-clustered table in a database management system. A table stores data that is organized into rows and columns. At least one column is designated as a key column. A particular row in the table is accessed based on a relationship between a specified key value and a predetermined range of key values associated with the key column. The table has slots for storing rows, and the slots are organized in accordance with the values of the predetermined range.

Abstract: A method, apparatus and article of manufacture, implementing the method, accesses rows in a range-clustered table in a database management system. A table stores data that is organized into rows and columns. At least one column is designated as a key column. A particular row in the table is accessed based on a relationship between a specified key value and a predetermined range of key values associated with the key column. The table has slots for storing rows, and the slots are organized in accordance with the values of the predetermined range.