NexusDB

From the beginning, NexusDB has been designed to completely utilize and support transaction-based processing.  In addition to standard transactions, NexusDB supports different types of transactions for a wide range of applications.  NexusDB supports these additional transaction types: failsafe, nested and snapshot transactions.

The transaction manager in NexusDB takes care of all transaction relevant management.

Isolation Levels

Open cursors outside the context of an explicit transaction have READ COMMITTED isolation. They can read from tables which are currently locked by an active transaction, no matter if that table is locked in shared or exclusive mode and will not place a lock of their own.

If a cursor belonging to a database with an active transaction is used to read or write it will join the context of that transaction and place a shared (read) or exclusive (write) lock or updates an existing shared lock to exclusive lock if required. Multiple transactions can own a shared lock or a single transaction can own a exclusive lock. This locking system guarantees SERIALIZABLE transaction isolation for cursors in the context of a transaction.