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< p > Library Version 11.2.5.2< / p >
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< th colspan = "3" align = "center" > DB_ENV-> set_lk_detect()< / th >
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< td width = "20%" align = "left" > < a accesskey = "p" href = "envset_lk_conflicts.html" > Prev< / a > < / td >
< th width = "60%" align = "center" > Chapter
The DB_LOCK Handle
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< h2 class = "title" style = "clear: both" > < a id = "envset_lk_detect" > < / a > DB_ENV-> set_lk_detect()< / h2 >
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< pre class = "programlisting" > #include < db.h>
int
DB_ENV-> set_lk_detect(DB_ENV *dbenv, u_int32_t detect); < / pre >
< p >
Set if the deadlock detector is to be run whenever a lock conflict
occurs, and specify what lock request(s) should be rejected. As
transactions acquire locks on behalf of a single locker ID, rejecting
a lock request associated with a transaction normally requires the
transaction be aborted.
< / p >
< p >
The database environment's deadlock detector configuration may also be
configured using the environment's < a href = "../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class = "olink" > DB_CONFIG< / a > file. The
syntax of the entry in that file is a single line with the string
"set_lk_detect", one or more whitespace characters, and the method
< span class = "bold" > < strong > detect< / strong > < / span > parameter as a string; for
example, "set_lk_detect DB_LOCK_OLDEST". Because the < a href = "../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class = "olink" > DB_CONFIG< / a >
file is read when the database environment is opened, it will
silently overrule configuration done before that time.
< / p >
< p >
The < code class = "methodname" > DB_ENV-> set_lk_detect()< / code > method configures a database environment,
not only operations performed using the specified < a class = "link" href = "env.html" title = "Chapter > DB_ENV< / a >
handle.
< / p >
< p >
The < code class = "methodname" > DB_ENV-> set_lk_detect()< / code > method may be
called either before or after environment open, but once it is set
it may not be changed again during the environment's lifetime.
< / p >
< p >
The < code class = "methodname" > DB_ENV-> set_lk_detect()< / code > < span >
< span >
method returns a non-zero error value on failure and 0 on success.
< / span >
< / span >
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< h3 class = "title" > < a id = "id3721344" > < / a > Parameters< / h3 >
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< h4 class = "title" > < a id = "id3721485" > < / a > detect< / h4 >
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< p >
The < span class = "bold" > < strong > detect< / strong > < / span > parameter configures the
deadlock detector. 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 > detect< / strong > < / span > parameter
is used to select which of those lock requests to reject. The
specified value must be one of the following list:
< / p >
< div class = "itemizedlist" >
< ul type = "disc" >
< li >
< p > < a id = "set_lk_detect_DB_LOCK_DEFAULT" > < / a >
< code class = "literal" > DB_LOCK_DEFAULT< / code >
< / p >
< p >
Use whatever lock policy was specified when the database environment
was created. If no lock policy has yet been specified, set the lock
policy to DB_LOCK_RANDOM.
< / p >
< / li >
< li >
< p > < a id = "set_lk_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 = "set_lk_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 = "set_lk_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 = "set_lk_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 = "set_lk_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 = "set_lk_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 = "set_lk_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 = "set_lk_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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< h3 class = "title" > < a id = "id3721907" > < / a > Errors< / h3 >
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< p >
The < code class = "methodname" > DB_ENV-> set_lk_detect()< / code > < span >
< span >
method may fail and return one of the following non-zero errors:
< / span >
< / span >
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< h4 class = "title" > < a id = "id3721798" > < / a > EINVAL< / h4 >
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An invalid flag value or parameter was specified.
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< h3 class = "title" > < a id = "id3721761" > < / 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 = "id3721816" > < / 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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