Abstract: Remastering of shared resources among nodes in a cluster, while minimizing the time that such resources are unavailable for access, comprises dividing the shared resources being remastered into multiple “windows” and freezing and remastering one window at a time. The remastering windows are defined over one or more buckets associated with a hash table of resources. In clusters with unequally sized hash tables, an enhancement to the fundamental windowing approach utilizes a functionally specific hashing algorithm and a hash table size constraint to ensure that the set of all resources that hash to a given bucket in a hash table of a given size will hash precisely to the same bucket, plus a set of higher buckets which are well defined, in a node that has a larger hash table.

Abstract: The state of locks maintained in volatile memory by the master for the resources are preserved after termination of the master. The locks are preserved by storing persistent copies of the locks. The persistently stored copies of the locks are accessible to other nodes in a multi-node system of the master. Locks for which persistent copies are stored in this way are referred to as persistent locks. A persistent copy of data is a copy that is stored in a form of memory that is able to store the copy after the volatile memory storing the data is unable to do so.

Abstract: Techniques are described herein for handling lock-related inconsistencies. As mentioned above, such inconsistencies occur when two or more sets of lock information, relating to the same resource, convey inconsistent information about locks requested and/or granted on that resource. In general, the techniques involve causing the locally-stored lock information about a resource to be sent to the master node of the resource. The master node of the resource compares the lock information thus received against the lock information maintained by the master node. Based on the comparison, the master node determines how to resolve the lock-related inconsistency, and sends messages to those nodes that need to change their local lock information for the resource. Once all of the lock information has been made consistent, the resource made available for access.

Abstract: A method and apparatus for managing locks in a database system is provided. A master node grants a lock on a first resource and a group of resources that includes the first resource to a first requester node. The requester node receives a mapping corresponding to the group of resources that may indicate that a lock already exists for a second resource in the group. If the requester node desires a lock on a resource located in the group, the requester node grants itself the lock without notifying the master node. A second requester node requests a lock for a particular resource in the group of resources. The first requester node grants the lock on the particular resource and updates the mapping to indicate that a different node holds a lock for the particular resource.

Abstract: Techniques are described for remastering shared resources among nodes in a cluster, while minimizing the number of resources that are unavailable for access (“frozen”) during the remastering operation. Only the resources that are being remastered from one node to one or more other nodes are frozen, whereas the other resources that are not being remastered are not frozen and are, therefore, still accessible. For example, in the context of a database cluster, there is no longer a need to freeze the entire database during a reconfiguration remastering operation. Consequently, during the remastering operation requests for access to the resources that are not being remastered can be processed and locks granted thereon.

Abstract: Techniques are provided for responding to the termination of a node by selecting another node, and assigning to the selected node the affinity relationships that existed between the terminated node and one or more objects. The resources that belong to the objects involved in the affinity relationships are remastered to the selected node. The selected node then performs recovery of the resources that had been opened by the terminated node and/or serves as a failover node to execute the transactions that had been executing on the terminated node.

Abstract: Techniques are provided for responding to the termination of a node executing one or more transactions by selecting another node to complete the transactions, and assigning to the selected node the affinity relationships that existed between the terminated node and the objects being accessed by said transactions.

Abstract: Techniques are described herein for handling lock-related inconsistencies. As mentioned above, such inconsistencies occur when two or more sets of lock information, relating to the same resource, convey inconsistent information about locks requested and/or granted on that resource. In general, the techniques involve causing the locally-stored lock information about a resource to be sent to the master node of the resource. The master node of the resource compares the lock information thus received against the lock information maintained by the master node. Based on the comparison, the master node determines how to resolve the lock-related inconsistency, and sends messages to those nodes that need to change their local lock information for the resource. Once all of the lock information has been made consistent, the resource made available for access. Because the lock-related inconsistency is resolved without restarting nodes, the availability required to correct the inconsistency.

Abstract: Remastering of shared resources among nodes in a cluster, while minimizing the time that such resources are unavailable for access, comprises dividing the shared resources being remastered into multiple “windows” and freezing and remastering one window at a time. The remastering windows are defined over one or more buckets associated with a hash table of resources. In clusters with unequally sized hash tables, an enhancement to the fundamental windowing approach utilizes a functionally specific hashing algorithm and a hash table size constraint to ensure that the set of all resources that hash to a given bucket in a hash table of a given size will hash precisely to the same bucket, plus a set of higher buckets which are well defined, in a node that has a larger hash table.

Abstract: Techniques are described for remastering shared resources among nodes in a cluster, while minimizing the number of resources that are unavailable for access (“frozen”) during the remastering operation. Only the resources that are being remastered from one node to one or more other nodes are frozen, whereas the other resources that are not being remastered are not frozen and are, therefore, still accessible. For example, in the context of a database cluster, there is no longer a need to freeze the entire database during a reconfiguration remastering operation. Consequently, during the remastering operation requests for access to the resources that are not being remastered can be processed and locks granted thereon.