The Transactions object in Microsoft SQL Server provides counters to monitor the number of transactions active in an instance of the Database Engine, and the effects of those transactions on resources such as the snapshot isolation row version store in tempdb. Transactions are logical units of work; a set of operations that must either all succeed or all be erased from a database in order to maintain the logical integrity of the data. All modifications of data in SQL Server databases are made in transactions.

When a database is set to allow snapshot isolation level, SQL Server must maintain a record of the modifications made to each row in a database. Each time a row is modified, a copy of the row as it existed before the modification is recorded in a row version store in tempdb. Many of the counters in the Transaction object can be used to monitor the size and rate of growth of the row version store in tempdb.

The Transactions object counters report all transactions in one instance of the Database Engine.