Transactions

Transactions can be started, committed or rolled back on a per connection basis:

use the toolbar button to start a transaction
use the toolbar button to commit the current transaction (apply all the changes)
use the toolbar button to abort the current transaction (forget all the changes)

A transaction may be started automatically when executing a SELECT statement which involves binary objects (BLOBs), and the transaction may be locked while the resulting data set is kept in memory (to get rid of a data set in a query execution perspective, clear the history item relating to the data set).