Abstract: A method and apparatus for fast refreshing a subquery snapshot creates the snapshot based on a first table and a second table according to a snapshot definition query, which contains one or more subqueries. Information about modifications to the first and second tables is stored in first and second log, respectively. When a refresh operation is initiated, the snapshot is refreshed by reconciling differences between the snapshot, the first table and second table according to the snapshot definition query, the first log, the second log, the first table, and the second table.

Abstract: An efficient set of indexes to cover a plurality of anticipated query types is determined by building a directed acyclic graph whose nodes correspond to anticipated query types. A minimum leaf spanning tree for the equivalent graph is determined by repeatedly finding an augmenting path for a current spanning tree and producing a reduced leaf spanning tree based on the current spanning tree and the augmenting path until an augmenting path can no longer be found. The leaves of the minimum leaf spanning tree indicate which indexes should be built.

Abstract: Communication costs are reduced in a distributed system that supports data replication with conflict detection by sending small values or nulls as replacements for field values that are not strictly used for replication or conflict detection. Specifically, nulls are propagated for new values of unmodified fields, old values of fields in unmodified groups of linked fields, and old values of fields for which conflict detection has been disabled. Flag values that indicate which actual old and new values were sent may be generated and propagated along with the replicated data.

Abstract: A method and apparatus for performing an administrative function on an object, replicated at a plurality of sites, suspends or "quiesces" replication activities at the granularity of an object group. Each object resides in an object group, and each object group has a status flag that indicates whether replication activities are quiesced. In response to detecting a request to perform an administrative function on an object, replication activities are suspended for the object group. Previous transactions are propagated to other sites. When each site has propagated all the previous transactions, the administrative function is performed and replication activities for the object group are resumed.

Abstract: A method and apparatus employs primary key values stored in a master table to drive a fast refresh mechanism for a snapshot defined on the master table. A primary key is a set of columns in the master table having a combined value that uniquely identifies each row in the master table. When rows of the master table are modified, the primary key values of the modified rows are recorded in a master log. In response to a fresh command, differences between the master table and snapshot are reconciled based on primary key values stored in the master table, the master log, and the snapshot.

Abstract: A method and apparatus for replicating data among sites is provided. The method allows changes to the same body of data to be replicated synchronously to some destination sites and asynchronously to other destination sites. Such mixed propagation configurations allow synchronous updating to selected remote copies of replicated data where data integrity is a high priority, and asynchronous propagation to remaining copies of replicated data in order to allow transactions to be committed locally regardless of whether the transaction is committed at a remote copy of the replicated data. The propagation mode is selectable by a user on a site-to-site basis for each replicated body of data, thus providing a mix of availability and consistency that is not possible in purely synchronous or purely asynchronous replication systems.

Abstract: An apparatus and method for providing adaptable and configurable conflict resolution within a replicated data environment is disclosed.