Abstract: When a request for a shutdown of a server (e.g. database server) is requested, existing sessions established for the clients are migrated to another server. Some sessions may not be migrated for various reasons; these sessions may be terminated without migrating them.

Abstract: A method and apparatus for managing sessions across the nodes of a multi-node system is provided. When a session is first initiated on any node of a multi-node system, a global session identifier is assigned to the session. The global session identifier uniquely identifies the session relative to all other sessions managed by the multi-node system. A session monitor may use the global session identifier to collect and store cumulative statistics about the activity of the session, regardless of which node of the multi-node system is currently managing the session, since the global session identifier uniquely identifies the session relative to all other sessions managed by the multi-node system. As a session may be uniquely identified across the lifetime of the session, the session state may be cleaned-up when the session ceases to be maintained, and the activity of the session during its lifetime may be analyzed.

Abstract: The present invention is directed to a method and mechanism for reducing the expense of data transmissions between a client and a server. According to an aspect of data prefetching is utilized to predictably retrieve information between the client and server. Another aspect pertains to data redundancy management for reducing the expense of transmitting and storing redundant data between the client and server. Another aspect relates to moved data structures for tracking and managing data at a client in conjunction with data redundancy management.

Abstract: A system and method for facilitating a remote procedure call (RPC) using an auto-evolvable RPC interface or record type (an “RPC structure”). Each field of an auto-evolvable RPC structure includes a version number and a default value. During a negotiation process, a client and a server exchange their highest version numbers, thereby indicating their RPC capabilities to each other. A higher or more recent version number may indicate a more recent release of the application comprising the RPC. During an RPC, when the client sends a structure to the server, or vice versa, and it has a more recent version, it may omit one or more fields that are not in the recipient's version. When the server receives a structure from the client, or vice versa, and it has a more recent version, it may populate an extra field (not in the sender's version) with its default value.

Abstract: A method and apparatus are provided for providing access to a remotely located nested object in a distributed database system. For example, a first server receives a request to access a complex database object that is not situated at the first server. When this occurs, the first server sends a second request to a second server. When the first server receives data in response to the second request, it detects whether the received data includes a reference to a nested object. If the first server detects a reference to a nested object, the first server modifies the received data by replacing the reference with a virtual reference to the nested object. The first server stores mapping data that associates the virtual reference with the reference and with an associated server, wherein the associated server is capable of resolving the reference. The first server forwards the modified data to the requestor.

Abstract: A session established for an application is suspended from an instance and later resumed on the server or a different server. When a session is suspended, its state is captured and persistently stored as a session image in a data repository, and the session is terminated. When the session is resumed, a new session is established on an instance, the session image of the session to resume is retrieved from the repository and restored to the newly established session. The suspension and resumption of a session may be initiated by an application, which may request the suspension and resumption of a session.

Abstract: The present invention is directed to a method and mechanism for reducing the expense of data transmissions between a client and a server. According to an aspect of data prefetching is utilized to predictably retrieve information between the client and server. Another aspect pertains to data redundancy management for reducing the expense of transmitting and storing redundant data between the client and server. Another aspect relates to moved data structures for tracking and managing data at a client in conjunction with data redundancy management.

Abstract: Techniques determine a quantity of rows to fetch based on memory available on a client computer and the fetch state of cursors. The techniques are used to determine a quantity of rows for “pre-fetching”. Under pre-fetching, rows in addition to those requested by an application are fetched from a database instance and stored in a “pre-fetch buffer”. The pre-fetch quantities are based on an amount of memory that is deemed available for pre-fetch buffers on a client computer and the number of cursors in the fetch state for a session at a given moment. Pre-fetching is used to hasten session migration. By fetching a quantity of rows that is larger than would be fetched if only the application-specified quantity were fetched, the fetch phase of a cursor is completed sooner. An earlier completion of the fetch phase of a session's cursors allows migration of the session to be completed sooner.

Abstract: A computer-implemented method of streaming a plurality of messages from a source queue to at least one destination queue over a computer network. The method may include steps of generating a remote procedure call, the remote procedure being configured to encapsulate at least header data, message data for each of the plurality of messages and an end of batch token, the header data being common to each of the plurality of messages and including an identification of the at least one destination queue, the end of batch token signaling that no further message data follows; sending the generated remote procedure call over the computer network to the destination queue identified in the header data, and dequeueing at least the message data for each of the plurality of messages from the source queue and streaming the dequeued messages over the network, and successively enqueueing each streamed message data into the at least one destination queue identified by the header data until the end of batch token is received.

Abstract: A system, method, computer program and system for suspending a result set and continuing from a suspended result set for a cursor is disclosed. The rows from a row source corresponding to the cursor result set are suspended into storage so that when a fetch is requested the data can be sent (continued) from the suspended storage and does not depend on the original cursor row source or session to be available.

Abstract: A system, method, computer program and system for suspending a result set and continuing from a suspended result set for a scrollable cursor is disclosed. The rows from a row source corresponding to the scrollable cursor result set are suspended into storage so that when a fetch is requested the data can be sent (continued) from the suspended storage and does not depend on the original scrollable cursor row source or session to be available.

Abstract: A system, method, computer program and system for suspending a result set and continuing from a suspended result set for transparent session migration is disclosed. The rows from a row source are suspended into storage, so that after session migration, the client fetches can transparently continue from the suspended result set.

Abstract: A method and system for implementing scrollable cursors is described. A multi-tier caching structure is maintained, in which a partial result set is cached at the client computer and a more-complete result set is cached at the server computer. If the cursor is scrolled in either the forward or backward directions, the partial result set cached at the client computer is first checked to see if requested data is present. If so, then the requested data is fetched from the client cache and the current position of the cursor is moved to the appropriate position in the result set. If the requested data is not present in the client cache, then those data items are fetched from the cache at the server computer.

Abstract: Techniques allow a client to be switched from a session on a server to another session on another server in a way that is a transparent to the application for which the initial session was established. Thus, under transparent session migration, a client is switched between sessions without executing application instructions tailored to accomplish the migration. Instead, a client-side interface component, through which the application interacts with the server, handles details of migration, modifying the internal state of the client-side interface component to effect the same. Legacy applications do not have to be modified in order to institute techniques described herein.

Abstract: Techniques allow a client to be switched from a session on a server to another session on another server in a way that is a transparent to the application for which the initial session was established. Thus, under transparent session migration, a client is switched between sessions without executing application instructions tailored to accomplish the migration. Instead, a client-side interface component, through which the application interacts with the server, handles details of migration, modifying the internal state of the client-side interface component to effect the same. Legacy applications do not have to be modified in order to institute techniques described herein.

Abstract: Techniques allow a client to be migrated from a session that has been established for a client on a server to another session on another server in a way that is a transparent to the application for which the initial session was established. The sessions are migrated under conditions in which a copy of session state of the session to migrate from the source node does not have to be captured and restored to a destination session.

Abstract: A method and apparatus is provided for providing access to a remotely located nested object in a distributed database system. According to one aspect of the invention, a first server receives a request to access a complex database object that is not situated at the first server. The first server translates the request to a remote mapped request, and transmits the remote mapped request to a second server. When the first server receives data in response to the remote mapped request, it detects whether the received data includes a reference to a nested object. If the first server detects a reference to a nested object, the first server modifies the received data by replacing the reference with a virtual reference to the nested object. The first server also stores mapping data that associates the virtual reference with the reference and with an associated server, wherein the associated server is capable of resolving the reference.

Abstract: A method and apparatus are provided for performing an array DML operation. During the performance of the operation on a data item in the array, and if an error occurs, then error information is stored and the array operation continues by performing the operation on the next data item in the array. The error is used to create update input data for the DML operation, and the update input data can be supplied during run-time of the program.

Abstract: A method and apparatus for is provided for efficiently transmitting multiple rows of data to a client station. The client station generates a query that is transmitted to a remotely located server, which in turn generates a query result. The server transmits the first row of data from the query result to the client. The remaining rows of data are transmitted by first calculating the difference between successive rows of data. Next, the server sends only the unique rows resulting from the calculated row difference to the client. The server also send an indication of the number of non-repeated value columns detected in order to allow reconstruction of the query result by the client station.