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<! "@(#)unlink.so 10.7 (Sleepycat) 9/29/98">
<!Copyright 1997, 1998 by Sleepycat Software, Inc. All rights reserved.>
<html>
<body bgcolor=white>
<head>
<title>Berkeley DB: DbLockTab::unlink</title>
<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btr
ee,hash,hashing,transaction,transactions,locking,logging,access method,access me
thods,java,C,C++">
</head>
<h1>DbLockTab::unlink</h1>
<hr size=1 noshade>
<tt>
<h3>
<pre>
#include <db_cxx.h>
<p>
static int
DbLockTab::unlink(const char *dir, int force, DbEnv *dbenv);
</pre>
</h3>
<h1>Description</h1>
<p>
The DbLockTab::unlink function destroys the lock table identified by the <i>directory</i>
<b>dir</b>, removing all files used to implement the lock table.
(The directory <b>dir</b> is not removed.)
<p>
If there are processes that have called <a href="../../api_cxx/DbLockTab/open.html">DbLockTab::open</a> without calling <a href="../../api_cxx/DbLockTab/close.html">DbLockTab::close</a>
(i.e., there are processes currently using the lock table), DbLockTab::unlink will fail
without further action, unless the force flag is set, in which case DbLockTab::unlink
will attempt to remove the lock table files regardless of any processes still using it.
<p>
The result of attempting to forcibly destroy the region when a process
has the region open is unspecified.
Processes using a shared memory region maintain an open file descriptor
for it.
On UNIX systems, the region removal should succeed
and processes that have already joined the region should continue to
run in the region without change,
however processes attempting to join the lock table will either fail or attempt
to create a new region.
On other systems (e.g., Windows/NT), where the <b>unlink</b>(2) system
call will fail if any process has an open file descriptor for the file, the
region removal will fail.
<p>
In the case of catastrophic or system failure, database recovery must be
performed (see <a href="../../utility/db_recover.html">db_recover</a>), or the DB_RECOVER and DB_RECOVER_FATAL
flags to <a href="../../api_cxx/DbEnv/appinit.html">DbEnv::appinit</a> must be specified.
Alternatively, if recovery is not required because no database state is
maintained across failures, it is possible to clean up a lock table by removing
all of the files in the directory specified to the <a href="../../api_cxx/DbLockTab/open.html">DbLockTab::open</a> function,
as no lock table files are created in any other directory.
Note, however, that this has the potential to remove files created by
the other Berkeley DB subsystems in the same database environment.
<p>
The DbLockTab::unlink
method either returns <b>errno</b> or throws an exception that
encapsulates an <b>errno</b> on failure, and 0 on success.
<p>
<h1>Errors</h1>
If a fatal error occurs in Berkeley DB, the DbLockTab::unlink method may fail and either
return DB_RUNRECOVERY or throw an exception encapsulating DB_RUNRECOVERY,
at which point all subsequent database calls will also fail in the same
way. Methods marked as returning <b>errno</b> will, by default, throw
an exception that encapsulates the error information. The default error
behavior can be changed, see <a href="../../api_cxx/DbException/class.html">DbException</a>.
<p>
The DbLockTab::unlink
method may fail and throw an exception
for any of the errors specified for the following Berkeley DB and C library
functions:
abort(3),
close(3),
<a href="../../api_cxx/DbEnv/version.html">DbEnv::version</a>,
fcntl(3),
fflush(3),
fprintf(3),
free(3),
fstat(3),
fsync(3),
getenv(3),
getpid(3),
getuid(3),
isdigit(3),
lseek(3),
malloc(3),
memcpy(3),
memset(3),
mmap(3),
munmap(3),
open(3),
pstat_getdynamic(3),
read(3),
shmat(3),
shmctl(3),
shmdt(3),
sigfillset(3),
sigprocmask(3),
stat(3),
strerror(3),
strlen(3),
sysconf(3),
unlink(3),
vfprintf(3),
vsnprintf(3),
and
write(3).
<p>
In addition, the DbLockTab::unlink
method may fail and throw an exception
or return <b>errno</b>
for the following conditions:
<dl compact>
<p><dt>EBUSY<dd>The shared memory region was in use and the force flag was not set.
</dl>
<p>
<h1>Class</h1>
<a href="../../api_cxx/DbLockTab/class.html">DbLockTab</a>
<p>
<h1>See Also</h1>
<a href="../../api_cxx/DbLockTab/close.html">DbLockTab::close</a>,
<a href="../../api_cxx/DbLockTab/detect.html">DbLockTab::detect</a>,
<a href="../../api_cxx/DbLockTab/get.html">DbLockTab::get</a>,
<a href="../../api_cxx/DbLockTab/id.html">DbLockTab::id</a>,
<a href="../../api_cxx/DbLockTab/open.html">DbLockTab::open</a>,
<a href="../../api_cxx/DbLockTab/stat.html">DbLockTab::stat</a>
DbLockTab::unlink
and
<a href="../../api_cxx/DbLockTab/vec.html">DbLockTab::vec</a>.
</tt>
</body>
</html>
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