Flush

Today I was asked to flush the database cache on one
of our test databases...

The proper command is:

ALTER SYSTEM FLUSH SHARED_POOL;

The command will clear out all SQL statements that are
located in the
Shared Pool Area. Oracle tracks of all SQL statements
that a user executes andstores parsed statements in
memory so that if a SQL statement has already been
executed then Oracle will not re-parse the statement.

There is an exception to this rule if the shared pool area
is not big enough, then the least recently used statements
(except for pinned packages) will be axed from memory.

By flushing the shared pool, all SQL statements are
removed from memory.