
106 Unleashing DB2 10 for Linux, UNIX, and Windows
Oracle enforces statement-level isolation. This means that all the data returned
by a query comes from a single point in time, that is, the time that the query
started. As a result, a query never sees changes made by other transactions
during its execution. Only data committed before the query began is available to
the query. Changes made by other transactions that commit during query
execution are invisible. As illustrated in Table 7-1, the phrase often associated
with this behavior is “readers do not block writers and writers do not block
readers.”
Cursor stability is the default isolation ...