That is BTEQ syntax. BTEQ has a simplistic scripting capability identified by the "." commands. It allows simple testing of conditions and branching forward in the script. It shows an example of testing the errorcode in a BTEQ script, though it only checks for zero so it would fail the script if it got a "does not exist" error. But the condition could be changed to exclude that error code. Or any error from the drop could simply be ignored.