Abstract: Disclosed is a mechanism, system, interface, and process to determine one or more life intervals when given a key. In addition, one or more life intervals can be determined for each key within a range of keys. This type of process is useful for auditing purposes or if it is desire to implement a query upon past versions when a key or range of keys is specified for the data for which past versions is desired. This facilitates algorithms, mechanisms, and processes to implement a query upon past versions.

Abstract: Techniques are described to allow a query to be registered as a persistent stored entity within the database, and to generate notifications as and when the query result changes continuously as long as the query continues to be registered with the database. According to one aspect, for a table referenced in a query, a filter condition is generated based, at least in part, on a predicate of the query. Then, the database server determines whether the filter condition is satisfied by either a before image of a row, or an after image of the row, that was modified by a transaction. If the filter condition is satisfied by either the before image or the after image, then the query is added to a first set of queries whose result sets may have been affected by the transaction. From among the first set of queries, a second set of queries that have result sets that were actually affected by the transaction is determined. Notifications are then sent based on the second set of queries.

Abstract: Disclosed are algorithms, mechanisms, processes, mechanisms, and systems to implement a query upon past versions. In one approach, the version query can be defined as either “rowid”-based access or non-rowid based access. With rowid based access, a given rowid is used to identify the data for which past versions are desired. Also disclosed is a mechanism, system, interface, and process to allow specification of a new table decoration clause to obtain one or more past version of one or more data items. The version query provides for a direct interface to get multiple versions of the row(s). In addition, information about the past versions can be retrieved and displayed along with the past versions.

Abstract: Disclosed is a mechanism, system, interface, and process to determine one or more life intervals when given a key. In addition, one or more life intervals can be determined for each key within a range of keys. This type of process is useful for auditing purposes or if it is desire to implement a query upon past versions when a key or range of keys is specified for the data for which past versions is desired. This facilitates algorithms, mechanisms, and processes to implement a query upon past versions.

Abstract: A query result set is an example of a type of body of data whose content is defined by a query. Modifications to a database can change the result of a query and therefore what the content of such a body of data, such as a result set, should be. Active Queries is an approach that enables a database server to detect database changes that alter the result of a query registered for a client and to notify a client of those changes. The notifications may be sent to, for example, a cache manager responsible for maintaining coherency of a result set cache generated by the query. The notification notifies the cache manager of when and/or what changes are needed to maintain the coherency of the cache.

Abstract: Processing a database statement received from a database client, which requests information about the timing of a last committed change to a row in a database table, comprises retrieving a logical time value that represents a commit time associated with the row and providing the value to the client. In one embodiment, providing the logical time value to the client is enabled by database infrastructure in which a virtual column is used to temporarily “store” the value so that the value can be manipulated as if the value resided in a column of the row. Performance of operations that involve the virtual column are processed similar to real columns, as if data was actually logically stored in the virtual column. For example, the virtual column can be used in condition clauses of database statements for concurrency control.

Abstract: Disclosed is a mechanism, system, interface, and process to allow specification of a new table decoration clause to obtain one or more past version of one or more data items. The version query provides for a direct interface to get multiple versions of the row(s). In addition, information about the past versions can be retrieved and displayed along with the past versions. Also disclosed are algorithms, mechanisms, and processes that are employed to implement a query upon past versions. In one approach, the version query can be defined as either “rowid”-based access or non-rowid based access. With rowid based access, a given rowid is used to identify the data for which past versions are desired. Also disclosed is a process for determining one or more life intervals when given a key.

Abstract: Methods and systems for automatically tuning the undo retention in a database system are disclosed. The undo tablespace may be of a fixed size or may be set to be automatically extended. If the undo tablespace is of a fixed size, the undo retention is set to a “best possible” undo retention, which is calculated based on statistical data stored in the system. If the undo tablespace is configured to be automatically extensible, the undo retention may be set to be greater than the duration of the longest running query in the system. The duration of the longest running query may be calculated in a distributed process in which each instance broadcasts information about its longest running query to other instances.

Abstract: A method and apparatus for selective removal of user data changes is provided. In one embodiment, the methodology is implemented by a logical recovery mechanism. Upon receiving a request to selectively remove user data changes stored in a database, the mechanism creates an empty set of transactions to be populated for selective removal, identifies one or more transactions and places them in the causal set of transactions. The mechanism further identifies other transactions that logically depend on any transaction already in the causal set of transactions. Finally, either while the causal set of transactions is being identified or after the identification is completed, the mechanism also determines user data changes made by the causal set of transactions. One or more compensating transactions may be generated by the logical recovery mechanism, which when executed, reverse the user data changes.

Abstract: One embodiment of the present invention provides a system for automatically classifying data in a database. During operation, the system receives and executes a database operation. Next, the system automatically determines if any data was modified as a result of executing the database operation. If so, for each data item that was modified, the system automatically determines if the data item is associated with a classification-rule. If so, the system automatically reclassifies the data item according to the classification-rule. If not, the system leaves a classification of the data item unchanged.

Abstract: Embodiments of the present invention include a method for performing a data uniqueness check in a set of sorted data blocks comprising accessing data to be inserted into the set of sorted data blocks, determining a proper data block of the set of sorted data blocks for which the data to be inserted should be located based on a first sorting key. The method further includes examining the proper data block for an existing data entry and if the proper data block is empty, the method further includes inserting the data to be inserted into the proper data block of the set of sorted data blocks.

Abstract: Techniques are disclosed for creating and using a filter index in order to identify registered queries whose result sets are likely to have been changed by changes made to tables. The filter index entries are based on filter conditions. The filter conditions are created based on predicates contained in the registered queries. The filter conditions may include exclusive predicates and join predicates. Join predicates that join a table T1 with a table T2 may be instantiated by replacing references to table T2 with values extracted from table T2. Various techniques are described for recognizing situations in which a query can be included in, or excluded from, the set of likely-changed queries, without fully evaluating the filter conditions that correspond to the queries.

Abstract: Techniques are described to allow a query to be registered as a persistent stored entity within the database, and to generate notifications as and when the query result changes continuously as long as the query continues to be registered with the database. According to one aspect, for a table referenced in a query, a filter condition is generated based, at least in part, on a predicate of the query. Then, the database server determines whether the filter condition is satisfied by either a before image of a row, or an after image of the row, that was modified by a transaction. If the filter condition is satisfied by either the before image or the after image, then the query is added to a first set of queries whose result sets may have been affected by the transaction. From among the first set of queries, a second set of queries that have result sets that were actually affected by the transaction is determined. Notifications are then sent based on the second set of queries.

Abstract: One embodiment of the present invention provides a system for automatically classifying data in a database. During operation, the system receives and executes a database operation. Next, the system automatically determines if any data was modified as a result of executing the database operation. If so, for each data item that was modified, the system automatically determines if the data item is associated with a classification-rule. If so, the system automatically reclassifies the data item according to the classification-rule. If not, the system leaves a classification of the data item unchanged.

Abstract: A method and apparatus for asynchronously storing transaction information related to a transaction is provided. A client process executing on a client may initiate a transaction request with a server. The server processes the transaction, commits the transaction, and writes transaction information associated with the transaction to memory without durably storing the transaction information. Thereafter, the server processing the transaction returns a message to the client that the transaction has been committed. A server process, which performed the transaction, may be reassigned to commit new work. Additional information that may be useful for the client about the result of the transaction may be contained in the message. Next, transaction information stored in memory is durably stored. A log writer may be used to durably store the transaction information to a log file. The client is subsequently notified that the transaction information has been durably stored at a client listening process.

Abstract: A method, system and computer program product for transparent support for distributed transactions in a clustered disk-sharing database environment is disclosed. In one approach, a method, a system and a computer program product are disclosed that disassociate a transaction with a session at a first resource manger, send a request to a second resource manager for the transaction that requires access to stored transaction information from prior requests for the transaction, determine whether the second resource manager has access to transaction information for the transaction stored using the session that has been disassociated with the transaction, obtain an identity of the first resource manager in data shared by the first and the second resource managers, and request access to the transaction information at the first resource manager.

Abstract: A method and apparatus for creating a target database on a target platform based on a source database on a source platform is provided. A target database is created on the target platform based on data, metadata (for example, data in the system tablespace and control files), and external objects (for example, password files and externally stored tables) comprised within the source database. Data and metadata stored in tablespaces of the source database are converted to the format compatible with the target platform. The conversion of the data and metadata may be performed either at the source database or the target database. Redo information and undo information of the source database are not copied from the source database to the target database. Certain files, e.g., a password files, and links to externally stored object may be recreated on the target database.

Abstract: Past versions of data in a distributed database system comprising multiple databases and associated database servers are queried using temporal database access mechanisms, where a request for data in a past state from a “remote” database can be received at a “local” database server and relevant portions of the request are passed to the remote server for processing. The processing performed by the remote server includes returning the requested data in the specified past state to the local server, or at least with enough information to reconstruct the data into the past state.

Abstract: Techniques are provided for guaranteed undo retention. The techniques include a database server attempting to store undo information in undo storage. In order to store the undo information, the database server may overwrite expired undo records; write to empty undo extents; allocate new undo extents and write to the newly-allocated extents; or overwrite unexpired undo records that do not have guaranteed undo retention. If an undo record does not have guaranteed undo retention, then the undo record may be overwritten before the expiration time has elapsed. If no undo extent is empty or unallocated, and if all of the undo records are unexpired and have guaranteed undo retention, then the database system has, at least temporarily, run out of usable and reusable space and an error may be reported to an appropriate party.

Abstract: In accordance with an embodiment of the present invention, a transaction tracking mechanism is provided by a database server cluster to keep track of a global state of a distributed transaction. The global state of the distributed transaction comprises one or more statuses that are associated with one or more transaction branches that are part of the distributed transaction. The global state may be associated with a global lock. Through using the global state in association with the global lock, problems such as partial commits, data inconsistency, access contentions and deadlocks may be avoided when the database server cluster processes the distributed transaction.