333 results about "Concurrency control" patented technology

A data structure, added to a modified form of the B^link-tree data structure, tracks delete states for nodes. The index delete state (D_X) indicates whether it is safe to directly access an index node without re-traversing the B-tree. The D_X state is maintained globally, outside of the tree structure. The data delete state (D_D) indicates whether it is safe to post an index term for a new leaf node. A D_D state is maintained in each level 1 node for its leaf nodes. Delete states indicate whether a specific node has not been deleted, or whether it may have been deleted. Delete states are used to remove the necessity for atomic node splits and chains of latches for deletes, while not requiring retraversal. This property of not requiring a retraversal is exploited to simplify the tree modification operations.

Various embodiments include one or more of systems, methods, software, and data structures that allow dual access to concurrent data in a database management system including uncommitted updated data. Some embodiments include a dual snapshot of data in a multi-version concurrency control style database, but the embodiments described herein are equally applicable to virtually any other type of database and database management system.

A system that facilitates concurrency control for a policy-based management system that controls resources in a distributed computing system. The system operates by receiving a request to perform an operation on a lockable resource from a controller in the distributed computing system. This controller sends the request in order to enforce a first policy for controlling resources in the distributed computing system. In response the request, the system determines whether the controller holds a lock on the lockable resource. If so, the system allows the controller to execute the operation on the lockable resource. If not, the system allows the controller an opportunity to acquire the lock. If the controller is able to acquire the lock, the system allows the controller to execute the operation on the lockable resource.

Portions of a B-tree index in a database are locked for concurrency control. In one example, hierarchical lock modes are provided that permit locking a key, a gap between the key and the next key, and a combination of the key and the gap. In another example, key range locking may be applied to the B-tree index using locks on separator keys of index nodes. In another example, key range locking may be applied to the B-tree index using locks on key prefixes.

A system and method for concurrency control in high performance database systems. Generally includes receiving a database access request message from a transaction. Then, generating an element that corresponds to the access request message. The element type is that of a read element, commit element, validated element, or restart element. The element is then posted to a read-commit (RC) queue. If the element is a commit element, an intervening validation of the transaction is performed. Upon the transaction passing validation the requested database access is performed.

Instead of executing a plurality of submitted transactions separately, each data item to be processed by the plurality of submitted transactions is retrieved only once, update operations of the plurality of transactions are executed consecutively on the retrieved data item in main memory, and only the last updated result is written in a database once.

Two-phase locking technique and timestamp technique are used for multi-operation processing providing concurrency control of transactions in order to execute multiple synthetic transactions concurrently.

Techniques have been developed whereby concurrency control mechanisms such as nested databases can be expressed in terms of operations implemented by various flexible transaction processing systems. For example, one such implementation of nested databases is particularly suitable for transaction processing systems that provides a lock delegation facility and which allow specification of ignore-conflict relationships between locking capabilities. By providing techniques that support movement of objects from a database to a subdatabase thereof, as well as termination (e.g., commit or abort) of transactions and databases (including subdatabases), transaction processing systems can provide advanced transaction models with unconventional concurrency control mechanisms. Some realizations allow specification of uses of parameters with lock modes and facilitate transformation of such uses into a form suitable for utilization in execution environments that support ignore-conflict relationships.

A variable-length binary string is utilized to encode node identifiers in a tree for an XML document object model. A general prefix encoding scheme is followed; a node identifier is generated by the concatenation of encodings at each level of a tree along a path from a root node to another particular node. Arbitrary insertions are supported without change to existing node identifier encodings. In addition, the method provides for document order when unsigned binary string comparison is used to compare encoded node identifiers. In support of sub-document concurrency control, prefix encoding provides a way to derive ancestor-descendant relationships among nodes in a tree. Lastly, the encoding method provides a natural pre-order clustering sequence, also known as depth-first clustering. If a prefix is applied to an encoding with a level number, starting with zero at the root, width-first clustering will result. A mixed clustering can also be supported.

A concurrent control method for a communication device embedded with Wi-Fi Direct includes dynamically adjusting a target beacon transmission time (TBTT) of a Wi-Fi Direct connection according to a time difference between the TBTT of the communication device and a nearest TBTT of a wireless local area network access point (WLAN AP) and whether a channel for the Wi-Fi Direct connection and a channel for the WLAN connection are different.

The invention discloses a high concurrent data transmission method based on RDMA (Remote Direct Memory Access). The method comprises the steps of establishing a graded buffer area before a client accesses a data transmission system; actively carrying out data transfer among a user buffer area, the graded buffer area and a remote memory area by the client when remote data read/write is carried out; and setting a lock field at the head part of each independent data block of the remote memory area by a server, wherein the lock field is used for concurrent control, when a plurality of clients concurrently read/write data, the concurrent control is carried out through a distributed lock protocol that the server locks locally and the clients unlock remotely. The method has the advantages that the data replication is reduced when a file is read/written, the processing pressure of the server is reduced, and the efficient concurrent control is provided.

An optimistic, latch-free index traversal (''OLFIT') concurrency control scheme is disclosed for an index structure for managing a database system. In each node of an index tree, the OLFIT shceme maintains a latch, a version number, and a link to the next node at the same level of the index tree. Index traversal involves consistent node read operations starting from the root. To ensure the consistency of node read operations without latching, every node update operation first obtains a latch and increments the version number after update of the node contents. Every node read operation begins with reading the version number into a register and ends with verifying if the current version number is consistent with the register-stored version number. If they are the same, the read operation is consistent. Otherwise, the node read is retried until the verification succeeds. The concurrency control scheme of the present invention is applicable to many index structures such as the B+-tree and the CSB+-tree.

The invention provides a concurrency control method, which comprises the following steps: judging whether locks conflicted with locks to be granted exist at a position of a transaction to be operated according to a lock relation table which is used for storing the relation of the transaction and the locks; granting the locks to the transaction according to a judgment result, and executing the transaction; and when the execution of the transaction is finished, releasing the locks held by the transaction, and granting the locks not needing continuously waiting in the released locks to other concurrency transactions. The invention also provides a concurrency control device, which comprises a judgment module, an execution module and a release module. The method solves the problems of low concurrency and poor system performance of transaction control by a concurrency method in related technology so as to improve the concurrency of the transaction control and concurrency control effect.

A control backplane replaces the traditional shared bus with a dedicated communication channel using a high-speed protocol, such as Ethernet. The resulting system may conduct several concurrent control sessions with clients and devices associated with the network switch. Removing the shared bus from the control plane also improves the reliability of the new system, because it is no longer susceptible to a single point of failure.

The present invention belongs to the computer technological field and provides a concurrent access control method, a terminal device, and a medium. The method includes the following steps that: a service access request initiated by a client is received; a function interface required to be called by the service access request and sub-function interfaces subordinated to the function interface are determined according to service parameters carried by the service access request; a pre-added concurrency control component is started, and the access control parameters of the sub-function interfaces subordinated to the function interface which are stored by the concurrency control component are read, wherein the access control parameters include a maximum allowed concurrent number; and the total number of the real-time accesses of the sub-function interfaces is obtained; and the service access request is rejected if the total number of the real-time accesses is greater than the maximum allowedconcurrent number. With the concurrent access control method, the terminal device, and the medium of the invention adopted, the possibility of the paralysis of a whole system can be decreased; the normal access of other sub-function interfaces is not affected; and the stability and reliability of the service system can be improved.

The embodiment of the invention discloses a multi-version concurrency control method in a database and a database system, which are mainly applied to the technical field of databases. The database system is provided with a data page chain of a page; the data page chain comprises a page compass of each version of the page; the page compass of one version of the page is used for pointing to another version of the page before last operation of the version of the page, so that the page can be directly rolled back to the page which needs to be read based on the data page chain of the page which is requested to be read if the time stamp of the current version of the page is greater than the time stamp including a reading service in a data reading request when pages in the database are read, a user is convenient to know the page in the database at any time and is convenient to inquire data of each version of the page in the database. Furthermore, the database system can realize roll-back of records efficiently through combination of the data page chain and a record chain, and can realize reading consistency.

A transaction creates a wait for dependency on a version in a main memory database implementing a multi-version concurrency control scheme. The wait for dependency allows the transaction to update the version while other transactions are reading the version. The multi-version concurrency control scheme also allows commit dependencies to be implementing concurrently with wait for dependencies. Commit dependencies allow a transaction to read an updated version before the updated version is committed.

The present teaching relates to concurrency control in log-structured merge (LSM) data stores. In one example, a call is received from a thread for writing a value to a key of LSM components. A shared mode lock is set on the LSM components in response to the call. The value is written to the key once the shared mode lock is set on the LSM components. The shared mode lock is released from the LSM components after the value is written to the key.