Transactions 
In the Performance user menu, you can find a display of active transactions.
Procedure
Open the Database Assistant (transaction DB50) or the liveCache Assistant (transaction LC10). Choose 
Problem Analysis 
Performance Transactions 
.
or
Open the DBA Cockpit (transaction DBACOCKPIT) and select Performance Transactions .
Result
You see an overview of the transactions.
More Information
DBA Cockpit: SAP MaxDB, Transactions
Concepts of the Database System, Transactions
SQL Reference Manual, Transactions