Abstract: Versioned metadata allows multiple versions of metadata for a given object to exist concurrently on a system thereby supporting the parallel execution of operations which would otherwise be mutually exclusive. Metadata updates are permitted while other objects maintain access to another version of the metadata through a versioning infrastructure. The versioning infrastructure allows the creation of new versions of metadata, maintains obsolete versions in the system as long as they are being used by any object, and deletes the obsolete versions once they are no longer in use.

Abstract: A system, method, computer program and article of manufacture for sharing metadata among cursors is provided. A metadata object marked as a versioned object can have multiple versions. Program units can share these versions of object metadata as opposed to copying the non-versioned object metadata into their memory. These program units may contain a pointer to an object's metadata but are otherwise void of the metadata information for the object. A locking protocol for the metadata ensures concurrency control and triggers dependency tracking. A locking protocol for the cursors controls cursor dependency status.

Abstract: A technique for automatically generating a report comprising normalized differences in performance statistics between two separate periods. In one embodiment of the invention, database performance statistics are collected on a periodic basis over various time periods. In order to accurately compare database system performance between two discrete periods of time, the difference in the performance statistics of each period are normalized prior to comparing the two periods with each other. By normalizing the statistical differences in each period prior to comparing the differences, periods of different lengths of time as well as different levels of database system load may be compared. In one embodiment, a report is automatically generated which lists the performance statistics being evaluated, the difference in the statistic between each period, the value of each statistical difference as normalized by database time, and the difference between the normalized values.