Abstract: Embodiments are directed to providing distributed database service upgrades of database server instances in a computer cluster using multiple database server instances and to monitoring and maintaining a distributed database service during upgrade. In an embodiment, each computer system in a computer cluster instantiates at least two different database server instances on each of the nodes in the cluster. The first database server instances are configured to operate using a current distributed database version and the second instances are configured to operate using a new, updated distributed database service version. The computer system receives an indication that the distributed database service is to be upgraded. Then, based on the received indication, the computer system migrates database replicas from the first database server instances to the second database server instances which operate the new, updated service version, substantially without user-visible downtime.

Abstract: Embodiments are directed to providing distributed database service upgrades of database server instances in a computer cluster using multiple database server instances and to monitoring and maintaining a distributed database service during upgrade. In an embodiment, each computer system in a computer cluster instantiates at least two different database server instances on each of the nodes in the cluster. The first database server instances are configured to operate using a current distributed database version and the second instances are configured to operate using a new, updated distributed database service version. The computer system receives an indication that the distributed database service is to be upgraded. Then, based on the received indication, the computer system migrates database replicas from the first database server instances to the second database server instances which operate the new, updated service version, substantially without user-visible downtime.

Abstract: Methods, systems, and computer-readable media of data storage that include storing page identities of individual pages and logical relationships between pages are disclosed. A particular system includes a plurality of data storage devices. A storage manager is configured to store data as pages at the data storage devices. Each page includes a page payload and a page identity. The storage manager is also configured to store one or more relationships indicating logical order between pages.

Abstract: A method of invalidating an unused log file in a database includes examining a discard log information storage area and determining if a discard log exists. If the discard log exists, the log is invalidated. The headers of each of the log files that have been fully invalidated are then invalidated. The discard log is then fully invalidated and a new log file may be generated on top of the discarded log. The method may be interrupted by a failure, a changeover, or crash and will be repeated until it completes.

Abstract: The resynchronization of multiple copies of a database after a divergence in transaction history in provided. In an illustrative implementation, algorithms are provided for synchronizing multiple copies of a database upon the occurrence of a divergence in transaction history. A data environment is provided having a database and a copy. The database environment operating in a manner where the database records some transactions and the copy recording some later transactions, but neither having an up-to-date set of data or log of data changes. In operation, the database and its copy compare transaction log sequence numbers to discern the changes database and/or database copy pages. During resynchronization, the database and/or its copy sends page specific information about changes that have not been performed on each other respectively. In this manner, the data environment may be resynchronized with minimal data transmitted and without a requiring a complete restoration of the database.

Abstract: A method of invalidating an unused log file in a database includes examining a discard log information storage area and determining if a discard log exists. If the discard log exists, the log is invalidated. The headers of each of the log files that have been fully invalidated are then invalidated. The discard log is then fully invalidated and a new log file may be generated on top of the discarded log. The method may be interrupted by a failure, a changeover, or crash and will be repeated until it completes.

Abstract: The resynchronization of multiple copies of a database after a divergence in transaction history in provided. In an illustrative implementation, algorithms are provided for synchronizing multiple copies of a database upon the occurrence of a divergence in transaction history. A data environment is provided having a database and a copy. The database environment operating in a manner where the database records some transactions and the copy recording some later transactions, but neither having an up-to-date set of data or log of data changes. In operation, the database and its copy compare transaction log sequence numbers to discern the changes database and/or database copy pages. During resynchronization, the database and/or its copy sends page specific information about changes that have not been performed on each other respectively. In this manner, the data environment may be resynchronized with minimal data transmitted and without a requiring a complete restoration of the database.

Abstract: To avoid possible data corruption resulting from restoring data to a database from a backup set that is not valid for the database, attempted restore operations are intercepted before they are performed. The backup set is examined to determine whether it was created from the same recovery fork on which the database resides or an descendant of that recovery fork. The backup set is only allowed to be applied to the database if the backup set was created from one of these recovery forks. If not, the backup set is not allowed to be applied to the database.

Abstract: A linked data structure verification system to verify the integrity of at least one linked data structure simultaneously by way of a verification setup phase and an integrity verification phase. Individual nodes are retrieved from a memory device and examined seriatim in optimal memory device location order. Nodes are retrieved and examined in optimal memory device location order for maximum memory device retrieval performance. Expected and/or actual node information about nodes in a given linked data structure are temporarily stored as records in an integrity verification table for only as much time as is necessary to verify any part of the node information prior to excising one or more unnecessary records from the integrity verification table.

Abstract: An apparatus is provided for passing respective messages from at least one writer process to multiple respective readers processes comprising: a storage buffer for storing a sequence of respective messages; and an access mechanism for providing respective multiple points of access for the respective reader processes to the sequence of respective messages; wherein for each of the multiple points of access, the access mechanism sequentially provides access to the respective messages of the sequence.

Abstract: In a multitasking, multiuser computer system, a server process temporarily impersonates the characteristics of a client process when the client process preforms a remote procedure call on the server process. Each process has an identifier list with a plurality of identifiers that characterize the process. The server process generates a new identifier list which is either the same as the client process's list, or is the union of the server's and the client's lists. Each object in the system can have an access control list which defines the identifiers that a process must have in order to access the object. The operation system has access checking software for enabling a selected process access to a specified object when the identifiers for the process match the list of identifiers in the access control list of the specified object. The server can therefore access all objects accessible to the client while the server is working for the client.

Abstract: In a multitasking, multiuser computer system, a server process temporarily impersonates the characteristics of a client process when the client process preforms a remote procedure call on the server process. Each process has an identifier list with a plurality of identifiers that characterize the process. The server process generates a new identifier list which is either the same as the client process's list, or is the union of the server's and the client's lists. Each object in the system can have an access control list which defines the identifiers that a process must have in order to access the object. The operation system has access checking software for enabling a selected process access to a specified object when the identifers for the process match the list of identifiers in the access control list of the specified object. The server can therefore access all objects accessible to the client while the server is working for the client.