Active Data Center

A data center and the TE and SM processes in it where the database workload runs. A database requires at least one active data center, containing at least one TE and at least one SM.

Asynchronous Commit

All database changes are replicated asynchronously to an Asynchronous SM in a remote passive data center, without the database slowing down due to inter-datacenter delay in communication between remote locations. In the event of a disaster, a recent, consistent snapshot of the database contents can be recovered and quickly put into service.

Asynchronous Storage Manager

An Asynchronous SM is an observer of all the storage groups that it serves. TEs perform asynchronous commit to an Asynchronous SM.


The number of bytes per second that a network connection can transmit.


The delay from when a message is sent into a network connection until the other end receives it.


The procedure for passing control of a database to a passive data center. It becomes the new active data center. Handoff is the response to a disaster that has eliminated all active data centers. This resets the database to the most recent consistent state available in archives in the passive data center.


An SM that passively receives changes to a storage group but does not participate in NuoDB’s performance-sensitive network protocols for that storage group. Latency between observers and other nodes has no effect on database performance. Transactions in the active data center do not depend on the latency for round-trip communication between the Transaction Engine and observers.

Passive Data Center

An additional data center containing Asynchronous Storage Manager processes that passively receive and record database changes. You can set up one or more passive data centers in remote locations for disaster recovery.


Transmission of database changes over the network from one TE or SM process to others.