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< p > Library Version 11.2.5.3< / p >
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< th colspan = "3" align = "center" > DB_ENV-> lock_detect()< / th >
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The DB_LOCK Handle
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< h2 class = "title" style = "clear: both" > < a id = "lockdetect" > < / a > DB_ENV-> lock_detect()< / h2 >
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< pre class = "programlisting" > #include < db.h>
int
DB_ENV-> lock_detect(DB_ENV *env,
u_int32_t flags, u_int32_t atype, int *rejected); < / pre >
< p >
The < code class = "methodname" > DB_ENV-> lock_detect()< / code > method runs one iteration of the deadlock
detector. The deadlock detector traverses the lock table and marks one
of the participating lock requesters for rejection in each deadlock it
finds.
< / p >
< p >
The < code class = "methodname" > DB_ENV-> lock_detect()< / code > method is the underlying method used by the
< a class = "link" href = "db_deadlock.html" title = "db_deadlock" > db_deadlock< / a > utility.
See the < a class = "link" href = "db_deadlock.html" title = "db_deadlock" > db_deadlock< / a >
utility source code for an example of using < code class = "methodname" > DB_ENV-> lock_detect()< / code > in
a IEEE/ANSI Std 1003.1 (POSIX) environment.
< / p >
< p >
The < code class = "methodname" > DB_ENV-> lock_detect()< / code > < span >
< span >
method returns a non-zero error value on failure and 0 on success.
< / span >
< / span >
< / p >
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< h3 class = "title" > < a id = "idp60554360" > < / a > Parameters< / h3 >
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< h4 class = "title" > < a id = "idp60565384" > < / a > flags< / h4 >
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The < span class = "bold" > < strong > flags< / strong > < / span > parameter is currently
unused, and must be set to 0.
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< h4 class = "title" > < a id = "idp60567832" > < / a > atype< / h4 >
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< p >
The < span class = "bold" > < strong > atype< / strong > < / span > parameter specifies which
lock request(s) to reject. The deadlock detector will reject the lock
request with the lowest priority. If multiple lock requests have the
lowest priority, then the < span class = "bold" > < strong > atype< / strong > < / span >
parameter is used to select which of those lock requests to reject.
It must be set to one of the following list:
< / p >
< div class = "itemizedlist" >
< ul type = "disc" >
< li >
< p > < a id = "detect_DB_LOCK_DEFAULT" > < / a >
< code class = "literal" > DB_LOCK_DEFAULT< / code >
< / p >
< p >
Use the default lock policy, which is DB_LOCK_RANDOM.
< / p >
< / li >
< li >
< p > < a id = "detect_DB_LOCK_EXPIRE" > < / a >
< code class = "literal" > DB_LOCK_EXPIRE< / code >
< / p >
< p >
Reject lock requests which have timed out. No other deadlock
detection is performed.
< / p >
< / li >
< li >
< p > < a id = "detect_DB_LOCK_MAXLOCKS" > < / a >
< code class = "literal" > DB_LOCK_MAXLOCKS< / code >
< / p >
< p >
Reject the lock request for the locker ID with the most locks.
< / p >
< / li >
< li >
< p > < a id = "detect_DB_LOCK_MAXWRITE" > < / a >
< code class = "literal" > DB_LOCK_MAXWRITE< / code >
< / p >
< p >
Reject the lock request for the locker ID with the most write locks.
< / p >
< / li >
< li >
< p > < a id = "detect_DB_LOCK_MINLOCKS" > < / a >
< code class = "literal" > DB_LOCK_MINLOCKS< / code >
< / p >
< p >
Reject the lock request for the locker ID with the fewest locks.
< / p >
< / li >
< li >
< p > < a id = "detect_DB_LOCK_MINWRITE" > < / a >
< code class = "literal" > DB_LOCK_MINWRITE< / code >
< / p >
< p >
Reject the lock request for the locker ID with the fewest write locks.
< / p >
< / li >
< li >
< p > < a id = "detect_DB_LOCK_OLDEST" > < / a >
< code class = "literal" > DB_LOCK_OLDEST< / code >
< / p >
< p >
Reject the lock request for the locker ID with the oldest lock.
< / p >
< / li >
< li >
< p > < a id = "detect_DB_LOCK_RANDOM" > < / a >
< code class = "literal" > DB_LOCK_RANDOM< / code >
< / p >
< p >
Reject the lock request for a random locker ID.
< / p >
< / li >
< li >
< p > < a id = "detect_DB_LOCK_YOUNGEST" > < / a >
< code class = "literal" > DB_LOCK_YOUNGEST< / code >
< / p >
< p >
Reject the lock request for the locker ID with the youngest lock.
< / p >
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< h4 class = "title" > < a id = "idp60583992" > < / a > rejected< / h4 >
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< / div >
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< p >
If the < span class = "bold" > < strong > rejected< / strong > < / span > parameter is
non-NULL, the memory location to which it refers will be set to the
number of lock requests that were rejected.
< / p >
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< h3 class = "title" > < a id = "idp60568272" > < / a > Errors< / h3 >
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< / div >
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< p >
The < code class = "methodname" > DB_ENV-> lock_detect()< / code > < span >
< span >
method may fail and return one of the following non-zero errors:
< / span >
< / span >
< / p >
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< h4 class = "title" > < a id = "idp60578560" > < / a > EINVAL< / h4 >
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< p >
An invalid flag value or parameter was specified.
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< h3 class = "title" > < a id = "idp60585072" > < / a > Class< / h3 >
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< p >
< a class = "link" href = "env.html" title = "Chapter > DB_ENV< / a > , < a class = "link" href = "lock.html" title = "Chapter > DB_LOCK< / a >
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< h3 class = "title" > < a id = "idp60587120" > < / a > See Also< / h3 >
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< p >
< a class = "xref" href = "lock.html#locklist" title = "Locking Subsystem and Related Methods" > Locking Subsystem and Related Methods< / a >
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