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<! "@(#)appsignals.so 10.14 (Sleepycat) 11/25/98">
<!Copyright 1997, 1998 by Sleepycat Software, Inc. All rights reserved.>
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<title>Berkeley DB Reference Guide: Programmer Notes</title>
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<h3>Berkeley DB Reference Guide: Programmer Notes</h3>
<p>
<h1 align=center>Application signal handling</h1>
<p>
When applications using Berkeley DB receive signals, it is important that they
exit gracefully, discarding any Berkeley DB locks that they may hold. This is
normally done by setting a flag when a signal arrives, and then checking
for that flag periodically within the application. As <b>Berkeley DB is
not reentrant</b>, the signal handler should not attempt to release locks
and/or close the database handles itself if there is any question at all
that Berkeley DB can be reentered. Reentering Berkeley DB is not guaranteed to work
correctly and the results are undefined.
<p>
If an application exits holding a lock, the situation is no different than
if the application crashed, and all applications participating in the
database environment must be shutdown, and then recovery must be
performed. If this is not done, the locks that the application held can
cause unresolvable deadlocks inside the database, and applications may
then hang.
<p>
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