Abstract: A method and apparatus for detecting split brain in a distributed system is provided. After determining that a rogue instance is no longer an active member of the cluster, a recovery instance detects activity associated with a redo log that is updated by the rogue instance to store log records that describe changes made by the rogue instance to data associated with the cluster.

Abstract: A standby database system or another replica data system replicates changes, made to data blocks at a source database system or another primary data copy, to replicas of the data blocks at the standby database system or other replica. While replicating the changes to the data blocks thereof, the standby database system (or other replica) receives queries (or reads) issued thereto and computes the queries based on data read from the data blocks thereof.

Abstract: A standby database system or another replica data system replicates changes, made to data blocks at a source database system or another primary data copy, to replicas of the data blocks at the standby database system or other replica. While replicating the changes to the data blocks thereof, the standby database system (or other replica) receives queries (or reads) issued thereto and computes the queries based on data read from the data blocks thereof.

Abstract: Detecting an operating condition in a multi-server data storage system. One or more of the data storage servers are designated with a status within the cluster. The designating may be performed by at least one of the data storage servers. The status is encoded into log data having records that report changes to the primary data storage performed by the cluster of data storage servers. The log data is transmitted from the primary data storage to the standby data storage system. The standby data storage system determines an operating condition of the cluster of data storage servers based, at least in part, on the status.

Abstract: Each of a plurality of Worker processes are allowed to perform any and all of the following tasks involving logged work items: (1) reading a subset of the work items from a log; (2) sequentially ordering work items for corresponding data objects; (3) applying a sequentially ordered set of work items to a corresponding data object; and (4) transmitting a subset of work items to a Worker process running on another database server in a cluster, if necessary. These tasks can be performed concurrently, at will, and as available, by the Worker processes. An improved checkpointing technique eliminates the need for the Worker processes to get to a synchronization point and stop. Instead, a Coordinator process examines the current state of progress of the Worker processes and computes a past point in the sequence of work items at which all work items before that point have been completely processed, and records this point as the checkpoint.

Abstract: A method for simulating different MTTR settings includes determining a simulated MTTR setting and providing a simulated checkpoint queue. The simulated checkpoint queue is associated with the simulated MTTR setting and is an ordered list of one or more elements. Each element represents a buffer, and the ordered list has a head and a tail. The method also includes providing a simulated write counter associated with the simulated MTTR setting. The method further includes, in response to detecting a change to a first buffer, checking if the first buffer is represented in the simulated checkpoint queue. If the first buffer is not represented in the simulated checkpoint queue, an element that represents the first buffer is linked to the tail of the simulated checkpoint queue. An MTTR advisory system includes a memory, one or more processors coupled to the memory, a simulated MTTR setting, a simulated checkpoint queue, and a simulated write counter. The simulated MTTR setting is maintained in the memory.