Oracle International Corporation

Douglas N Surber

Tong Zhou

Carol L Colrain

Jean De Lavarene

Kevin S Neel

Ashok Shivarudraiah

Nancy Reiko Ikeda

Stefan Heinrich Roesch

Mark Dilman

Wei Ming Hu

Leonid Novak

Vidya Hegde

Paul Parkinson

Saurabh Kumar Verma

Ilya Taranov

Yuri Dolgov

Lik Wong

Todd Jeffery Little

Vivekanandhan Raja

Ravi Shankar Thammaiah

David Scott Merrill

Stephen Felts

Rajkumar Arockia Irudayaraj

Jonathan Giloni

Edward Shirk

Arturo Ismael Quinto

Garret Frederick Swart

Mark Jungerman

Saurabh Verma

Ilesh Garish

Pankaj Chand

Michael McMahon

Pablo Silberkasten

Rohan Ankalikar

Manoj Dhanapal

Paul Lo

Wei Hu

Nancy R Ikeda

Techniques are disclosed herein for identifying, recording and restoring the state of a database session and various aspects thereof. A session template data structure is generated that includes session attribute values describing various aspects of the session that is established between a client system and a database management system (DBMS and enables the client system to issue to the DBMS commands for execution. Based on the session attribute values, DBMS may generate a template identifier corresponding to the session template data structure. The template identifier may be stored in an association with the session state that it partially (or in whole) represents. In an embodiment, when another state of a session is captured, if the template identifier for the state is the same, then rather than storing the attribute-value pairs for the other state, the template identifier is further associated with the other state. In an embodiment, a request boundary is detected where the session is known to be at a recoverable point. If recovery of the session is needed, the session state is restored, and replay of commands start from this point. Each command replayed is verified to produce the same session state as it produced by the original execution. If the session is determined to be a safe point, then all the commands recorded for replay prior to the safe point may be deleted. In an embodiment, the template is used to set the initial state when borrowing from a session pool. The state tracking is also used to identify that the session can be failed over safely during planned operation as the session is unlikely to drain by itself even when not used.

Session state tracking

In accordance with an embodiment, described herein are systems and methods for providing direct access to a sharded database. A shard director provides access by software client applications to database shards. A connection pool (e.g., a Universal Connection Pool, UCP) and database driver (e.g., a Java Database Connectivity, JDBC, component) can be configured to allow a client application to provide a shard key, either during connection checkout or at a later time; recognize shard keys specified by the client application; and enable connection by the client application to a particular shard or chunk. The approach enables efficient re-use of connection resources, and faster access to appropriate shards.

System and method for providing direct access to a sharded database

Techniques are provided for processing a database command in a sharded database. The processing of the database command may include generating or otherwise accessing a shard key expression, and evaluating the shard key expression to identify one or more target shards that contain data used to execute the database command.

Automatic derivation of shard key values and transparent multi-shard transaction and query support

Techniques are disclosed herein for identifying, recording and restoring the state of a database session and various aspects thereof. A session template data structure is generated that includes session attribute values describing various aspects of the session that is established between a client system and a database management system (DBMS and enables the client system to issue to the DBMS commands for execution. Based on the session attribute values, DBMS may generate a template identifier corresponding to the session template data structure. The template identifier may be stored in an association with the session state that it partially (or in whole) represents. In an embodiment, when another state of a session is captured, if the template identifier for the state is the same, then rather than storing the attribute-value pairs for the other state, the template identifier is further associated with the other state. In an embodiment, a request boundary is detected where the session is known to be at a recoverable point. If recovery of the session is needed, the session state is restored, and replay of commands start from this point. Each command replayed is verified to produce the same session state as it produced at original execution. If the session is determined to be a safe point, then all the commands recorded for replay prior to the safe point may be deleted. In an embodiment, the template is used to set the initial state when borrowing from a session pool The state tracking is also used to know that the session can be failed over safely during planned operation as the session is unlikely to drain by itself even when not used.

Session templates

In accordance with an embodiment, the system enables access to a sharded database using a cache and a shard topology. A shard-aware client application connecting to a sharded database can use a connection pool (e.g., a Universal Connection Pool, UCP), to store or access connections to different shards or chunks of the sharded database within a shared pool. As new connections are created, a shard topology layer can be built at the database driver layer, which learns and caches shard key ranges to locations of shards. The shard topology layer enables subsequent connection requests from a client application to use a fast key path access to the appropriate shard or chunk.

System and method for providing access to a sharded database using a cache and a shard technology

In accordance with an embodiment, a system enables multidimensional search within a resource pool, to support complex borrow operations such as, for example, specifying ranges for particular connection properties. As threads access the pool, attempting to borrow connections having particular connection properties, one or more skipped pool elements can be represented as skip lists within a k-dimensional tree (KD-tree) or other data structure that enables searching across multiple dimensions. In response to receiving a request to borrow a connection having particular connection properties, a multidimensional search can be performed within the KD-tree to determine the availability of a connection having the requested properties.

System and method for multidimensional search with a resource pool in a computing environment

Techniques are described for closing one or more connections with a database management system (DBMS) as part of a planned operation such as maintenance and load balancing. In an embodiment, a request is received for a planned operation of a database server of a DBMS that requires releasing and migrating database sessions. Over a database connection with the database server, the DBMS or a Client-Driver on the client system that interfaces with the DBMS, may receive request(s) from the client system. Based on the request(s), a safe point, for the database connection with the database server, at which the database connection of the client system with the database server can be closed without affecting the success of execution of next one or more command that the client system intended to request the DBMS to execute on the database server, is determined. In an embodiment, in response to the request(s), the DBMS and/or Client-Driver, while the connection is valid, provide to the client system an invalid status for a connection test request. Such a response may cause the client system to use a different database connection to connect with the DBMS. After returning the response to the client system, the DBMS and/or Client-Driver causes the database session with the DBMS to close. In an embodiment, for database sessions to be released, the DBMS identifies a safe point in a database session by a detected request boundary or where the session states are determined to be recoverable or the failover is determined to be expected to succeed. At such a safe point, all database session states are known, and failing the session over to another database instance offering the requested service can be performed safely and transparent to applications.

Safe release of database sessions for planned maintenance operations

In accordance with an embodiment, described herein is a system and method for high availability and load balancing in a database environment. A transparency engine can be provided between client applications and a database, and can operate as a proxy engine for the database and as a session abstraction layer for the client applications, to enable the client applications to utilize database features provided by the connection pool without code changes to the client applications. The transparency can keep track of session states, request boundaries and cursors to efficiently reuse the database connections across the client applications. The transparency engine can use the request boundaries and indicators from the database to detect safe places to drain database connections in the event of database outages.

System and method for high availability and load balancing in a database environment

In accordance with an embodiment, described herein is a system and method for use of immutable accessors with dynamic byte arrays. In accordance with an embodiment, a database driver provides access by software applications executing at an application server to data at a database, including associating a result set cache manager with a pool of result set caches. Each result set cache can be associated with one or more immutable accessors. In response to receiving a request from an application, to access a set of data, the set of data from the database is received into a particular result set cache. In response to receiving a subsequent request for a same set of data, from a same or another application using a same or another database connection, access is provided to the immutable accessor associated with the particular result set cache, for use in accessing the data therein.

System and method for use of immutable accessors with dynamic byte arrays

A system and method for reducing communications overhead in a distributed transaction processing environment such as an XA environment. In accordance with an embodiment communication overhead is reduced in a transaction by deferring a transaction end communication. The deferred transaction end communication is determined from a subsequent XA transaction communication thereby reducing the number of networks calls required for each transaction and enhancing system performance.

System and method for reducing communications overhead in a distributed transactions environment by modifying implementation of the transaction end function

In accordance with an embodiment, described herein is a system and method for use of a non-blocking process with a resource pool, for example a connection pool, or another type of computing environment. A generic wait-free approach can be used with a variety of different types of resource pools and pool elements. Threads which require access to a collection of resources do not have to wait for a lock on that collection of resources to become available. Although a borrowing thread may still be required to wait for a particular resource to be released, the wait-free approach allows the thread to browse through a list of available resources. The approach can be used with connection pools, or with other types of computing environments, to provide improved scalability in such systems.

System and method for use of a non-blocking process with a resource pool in a computing environment

A system and method is described for database split generation in a massively parallel or distributed database environment including a plurality of databases and a data warehouse layer providing data summarization and querying functionality. A database table accessor of the system obtains, from an associated client application, a query for data in a table of the data warehouse layer, wherein the query includes a user preference. The system obtains table data representative of properties of the table, and determines a splits generator in accordance with one or more of the user preference or the properties of the table. The system generates, by the selected splits generator, table splits dividing the user query into a plurality of query splits, and outputs the plurality of query splits to an associated plurality of mappers for execution by the associated plurality of mappers of each of the plurality of query splits against the table.

System and method for data transfer from JDBC to a data warehouse layer in a massively parallel or distributed database environment

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Redwood City, CA, United States of America

Douglas N Surber