In one example method, a second memory stores data in a database, and the second memory is a memory independent of a first device and a second device. When determining that a database service needs to be switched, the first device may migrate a redo log of the database from a first memory of the first device to the second memory. The second device migrates the redo log from the second memory to a third memory of the second device, and the first device and the second device perform operating system status migration online.

With the method for snapshotting metadata, in response to reaching a current snapshot moment, a second basic version number of a binary search tree in a database at the current snapshot moment is generated according to a first basic version number at a previous snapshot moment; during a process from the current snapshot moment to a next snapshot moment, whenever metadata in the database is updated, the binary search tree is updated according to the updated metadata, and an updated version number of the binary search tree after each update is generated according to the second basic version number; and in response to reaching the next snapshot moment, a snapshot operation is performed on binary search trees corresponding to all version numbers generated between the current snapshot moment and the next snapshot moment to generate snapshot information of the current snapshot moment.

The subject technology retrieves information related to a set of instances of compute service managers, each instance of a particular compute service manager being associated with a set of virtual warehouses. The subject technology filters the information to determine a set of candidates from the set of instances of compute service managers. The subject technology sorts the set of candidates based at least in part on each workload of each of the set of candidates. The subject technology selects a candidate compute service manager from the set of instances of compute service managers to issue a query restart by randomly selecting an execution node, the execution node being included in a particular virtual warehouse associated with the candidate compute service manager, the selecting facilitating improving utilization of cluster resources and improving query execution on the selected candidate compute service manager.

Techniques are disclosed herein for identifying, recording and restoring the state of a database session and various aspects thereof. A session template data structure is generated that includes session attribute values describing various aspects of the session that is established between a client system and a database management system (DBMS and enables the client system to issue to the DBMS commands for execution. Based on the session attribute values, DBMS may generate a template identifier corresponding to the session template data structure. The template identifier may be stored in an association with the session state that it partially (or in whole) represents. In an embodiment, when another state of a session is captured, if the template identifier for the state is the same, then rather than storing the attribute-value pairs for the other state, the template identifier is further associated with the other state. In an embodiment, a request boundary is detected where the session is known to be at a recoverable point. If recovery of the session is needed, the session state is restored, and replay of commands start from this point. Each command replayed is verified to produce the same session state as it produced at original execution. If the session is determined to be a safe point, then all the commands recorded for replay prior to the safe point may be deleted. In an embodiment, the template is used to set the initial state when borrowing from a session pool The state tracking is also used to know that the session can be failed over safely during planned operation as the session is unlikely to drain by itself even when not used.

Methods, storage systems and computer program products create a transactionally consistent backup of a database by generating, during a time period beginning with a first time and ending with a second time, a copy of the database including multiple tables. During the time period, queries that request updates to the tables are periodically generated and conveyed to a software system managing the database, responses including updates to the tables are received responsively to the periodic queries, and the received updates are stored to a journal. A set of the updates not stored in the copy are identified, in the journal, and copy of the database is updated with the updates so as to ensure that the copy includes the transactionally consistent backup of the database.

An automated method is provided for use when replacing a currently operating data replication engine in a first system with a new data replication engine in the first system in a bidirectional data replication environment. The currently operating data replication engine in the first system and the new data replication engine in the first system replicates first database transactions from an audit trail of a first database in the first system to a second database in a second system. The new data replication engine in the first system generating a list of active database transactions in the first system, and sends the list of active database transactions to the new data replication engine in the second system as a first token. The new data replication engine in the second system receives the first token, fetches a transaction event from an audit trail of second database, and replicates the fetched transaction event to the new data replication engine of the first system when the fetched transaction event does not match a transaction on the list in the first token. These steps are repeated during operation of the new data replication engine of the second system. The currently operating data replication engine in the first system is stopped from replicating first database transactions when all of the transactions on the list of active database transactions that were generated have been replicated to the second system.

Electronic communications between a client device and a server device are improved by providing a middleware component that incorporates electronic data read and/or written to a database in a hybrid data structure. The hybrid structure is further designed to allow for “NULL” or other pre-defined data values when one or more data fields are unavailable or erroneous. The client device, in turn, can be configured to check for the pre-defined data values in certain fields and to gracefully process such values. The hybrid structure with pre-defined error values therefore provides for very efficient data transmittal and processing, while retaining the ability to handle errors or other unusual situations relating to the data.

Described herein is a method, system, and non-transitory computer readable medium for helping customers in accessing data through an application from a replica database, detecting whether the replica database, zone of availability of the replica database, or geographical region encompassing the zone of availability is experiencing an outage or other failure, and re-routing traffic to a backup replica database accordingly. To assess the status of the database, metrics are pushed in a secure manner from a private subnet to a public-facing monitoring agent, achieving a clear segregation of private subnet and public facing components. Further, circuit-breaker logic is included for preventing failure during updating DNS addresses during the re-routing process.

A multi-tenant computing system provides services to a number of different tenant organizations. To address the problem of failure of portions of the system, the hardware infrastructure of the system is located at a number of different geographical locations. The various tenants are assigned to one of a set of “cells,” each cell corresponding to one of the geographical locations. Additionally, each cell has another one of the cells assigned to it as a backup cell, and the data of each cell is replicated within its assigned backup cell. At system run time, if a failure is detected within one of the cells, the network redirection is used within the multi-tenant system to reflect that the backup cell for the failing cell is now handling requests for the failing cell. Upon determination that the failing cell has been repaired and is now again correctly functioning, the network redirection is no longer employed, such that the (formerly) failing cell again handles its own requests.

Techniques are provided for analyzing events incoming through a message broker and configuring a database schema for storing the events based on the analysis. The analysis is performed on all the attributes of the incoming events with reference to a primary identifier of an event source. The analysis determines the characteristics of the attributes, which facilitates development of the database schema with availability, accuracy, existence, and other factors of various attributes. Analysis is supported for various formats of events, such as AVRO, XML, complex JSON, etc. In some examples, the attributes of interest for database schema generation can be provided via a configuration for the respective databases including relational, time-series, analytical, graph, etc. Also, if a given database supports direct ingestion of data through the message broker, then the ingestion specification can be generated.