46 results about "Log sequence number" patented technology

A computer program product and system for committing transactions in a distributed system are provided. The method, computer program product, and system provide for receiving a request from a client to commit a transaction at a coordinator node in the distributed system, tracking a tail log sequence number for every other node in the distributed system, determining a max log sequence number associated with the transaction for each participant node in the distributed system, and committing the transaction at the coordinator node when the tail log sequence number for each participant node is greater than or equal to the max log sequence number associated with the transaction at the respective participant node.

An architecture and implementation for losslessly restarting subsystems in a distributed file system is described. By partitioning functionality and logging appropriately across the kernel and user-level boundaries on a client, the user-level subsystem may be made losslessly restartable. Practical mechanisms for supporting state-based recovery in replicated state machines and like replica are described. In particular, each client daemon may include an operations log and an applied log sequence number. Each client driver may include a potentially different operations log. Each client daemon may be configured to request logged operations associated with log sequence numbers in one or more ranges specified by a specification that includes the applied log sequence number. The requested logged operations may reside in the operations log maintained by a client driver. Each client daemon may operate in accordance with user-level constraints and each client driver may operate in accordance with kernel-level constraints.

The present invention expounds upon the ANSI “read committed” isolation level by allowing readers to read committed data without waiting for a concurrent writer to the data to finish. The method returns a last committed version of the data as it existed prior to changes made by the concurrent writer. Only two versions of any data record are required to be stored in the record data store, the last committed version and the current version. The last committed version may be generated from an undo log record. Locating the appropriate undo log record may be accomplished by storing a log sequence number in a lock data structure associated with the requested data record. A transaction flag may also stored in the lock data structure to facilitate generating the last committed version. The method may also utilize one or more locks to detect a concurrent writer to the requested data.

A data replication method can begin with the detection of an inconsistency between records of a target table and corresponding records of a source table of a relational database management system (RDBMS) performing a parallel apply replication by an improved data replication manager. The target table can be a copy of the source table, both of which include multiple unique constraints and indexes. A timeframe that encompasses the records of the target table having the inconsistency can be determined. The timeframe can utilize a commit timestamp or a log sequence number. Consistency between the target table and the source table can be automatically restored for the determined timeframe through use of a reactive-apply process. Data suppression for updates is automatically restored once the copy is consistent. Transactions performed upon the target table by the reactive-apply process can be performed in parallel. Service at the source table and the target table can be uninterrupted.

Embodiments of the invention generally relate to data processing systems and more particularly to high availability data processing systems. A primary server may share a storage device with one or more clone systems. Each clone generally replicates the state of the primary server, but relies on the same disk-based storage as the primary server. Thus, the clone systems may provide a shadow of the primary server, ready to take over should the primary server fail. The clone systems may access a log file that includes entries reflecting the actions performed by the primary system. The primary server may flush entries from a log buffer maintained on the primary server to a log file stored on the shared disk-based storage. The primary server may also send a log sequence number to the clone systems, and the clone systems periodically transmit a log sequence number back to the primary server indicating how far through the log file a clone system has progressed.

The present invention relates to the technical field of backup and restoration of databases, in particular to a hot backup method for MySQL databases, comprising: when the backup starts, first checking the log sequence number of the MySQL database, and then backing up the data files of the MySQL database; During the process, the redo log of the MySQL database is checked cyclically at the same time, and the modification of the data file is backed up during the backup process. The log sequence number in the redo log is greater than the log sequence number at the beginning of the backup. The log is recorded in a file and stored in the shared storage Device; after the backup is completed, record the log sequence number at this time to prepare for the next backup. The invention also provides a hot backup system of MySQL database. Compared with the prior art, the technical scheme of the present invention has fast backup speed and fast recovery speed, overcomes the shortcoming that the MySQL database must be stopped before backup, and has less impact on the MySQL database business.

Embodiments of the present invention provide a DB2 database data synchronization update method and device. The method includes: creating a data detailed address storage column according to the table to be updated to be synchronized, an S lock on the table to be updated to be synchronized, acquiring the current log sequence number LSN of the source DB2 database as the starting LSN of the table to be updated to be synchronized, and releasing the S lock; Obtain the result set of the table to be synchronized and updated, send the result set to the target database for storage, and obtain the current LSN of the source DB2 database as the end LSN of the table to be synchronized and updated; receive the initialization data sent by the source synchronization update service, on the target The database inserts ROWID into the data detailed address storage column, initializes the data of the table to be updated synchronously; starts the real-time data synchronization update service, and sends the changes of the source DB2 database to the target database for data synchronization update. Various embodiments of the present invention can avoid the adverse effects caused by the S lock on the table to be synchronously updated for a long time under the premise of ensuring the data consistency of the target database.