2
<!--Copyright 1997-2002 by Sleepycat Software, Inc.-->
3
<!--All rights reserved.-->
4
<!--See the file LICENSE for redistribution information.-->
7
<title>Berkeley DB: DbEnv::lock_vec</title>
8
<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
9
<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++">
12
<a name="2"><!--meow--></a>
13
<table width="100%"><tr valign=top>
15
<h1>DbEnv::lock_vec</h1>
18
<a href="../api_cxx/c_index.html"><img src="../images/api.gif" alt="API"></a><a href="../reftoc.html"><img src="../images/ref.gif" alt="Ref"></a>
23
#include <db_cxx.h>
26
DbEnv::lock_vec(u_int32_t locker, u_int32_t flags,
27
DB_LOCKREQ list[], int nlist, DB_LOCKREQ **elistp);
30
<p>The DbEnv::lock_vec method atomically obtains and releases one or more locks
31
from the lock table. The DbEnv::lock_vec method is intended to support
32
acquisition or trading of multiple locks under one lock table semaphore,
33
as is needed for lock coupling or in multigranularity locking for lock
35
<p>The <b>locker</b> argument specified to DbEnv::lock_vec is an unsigned
36
32-bit integer quantity. It represents the entity requesting or releasing
38
<p>The <b>flags</b> value must be set to 0 or
41
<p><dt><a name="DB_LOCK_NOWAIT">DB_LOCK_NOWAIT</a><dd>If a lock cannot be granted because the requested lock conflicts with
43
return DB_LOCK_NOTGRANTED or throw a
44
<a href="../api_cxx/lockng_class.html">DbLockNotGrantedException</a> immediately instead of waiting for
45
the lock to become available. In this case, if non-NULL,
46
<b>elistp</b> identifies the request that was not granted, or, if an
47
exception is thrown, the index of the request that was not granted can
48
be found by calling DbLockNotGrantedException.get_index.
50
<p>The <b>list</b> array provided to DbEnv::lock_vec is typedef'd as
51
DB_LOCKREQ. A DB_LOCKREQ structure has at least the following fields.
52
In order to ensure compatibility with future releases of Berkeley DB, all
53
fields of the DB_LOCKREQ structure that are not explicitly set should
54
be initialized to 0 before the first time the structure is used. Do
55
this by declaring the structure external or static, or by calling
58
<p><dt>lockop_t <a name="op">op</a>;<dd>The operation to be performed, which must be set to one of the
61
<p><dt><a name="DB_LOCK_GET">DB_LOCK_GET</a><dd>Get the lock defined by the values of the <b>mode</b> and <b>obj</b>
62
structure fields, for the specified <b>locker</b>. Upon return from
63
DbEnv::lock_vec, if the <b>lock</b> field is non-NULL, a reference
64
to the acquired lock is stored there. (This reference is invalidated
65
by any call to DbEnv::lock_vec or <a href="../api_cxx/lock_put.html">DbEnv::lock_put</a> that releases the
67
<p><dt><a name="DB_LOCK_GET_TIMEOUT">DB_LOCK_GET_TIMEOUT</a><dd>Identical to DB_LOCK_GET except that the value in the <b>timeout</b>
68
structure field overrides any previously specified timeout value for
69
this lock. A value of 0 turns off any previously specified timeout.
70
<p><dt><a name="DB_LOCK_PUT">DB_LOCK_PUT</a><dd>The lock to which the <b>lock</b> structure field refers is released.
71
The <b>locker</b> argument, and <b>mode</b> and <b>obj</b> fields
73
<p><dt><a name="DB_LOCK_PUT_ALL">DB_LOCK_PUT_ALL</a><dd>All locks held by the specified <b>locker</b> are released. The
74
<b>lock</b>, <b>mode</b>, and <b>obj</b> structure fields are
75
ignored. Locks acquired in operations performed by the current call to
76
DbEnv::lock_vec which appear before the DB_LOCK_PUT_ALL
77
operation are released; those acquired in operations appearing after
78
the DB_LOCK_PUT_ALL operation are not released.
79
<p><dt><a name="DB_LOCK_PUT_OBJ">DB_LOCK_PUT_OBJ</a><dd>All locks held on the object <b>obj</b> are released. The
80
<b>locker</b> argument and the <b>lock</b> and <b>mode</b> structure
81
fields are ignored. Locks acquired in operations performed by the
82
current call to DbEnv::lock_vec that appear before the
83
DB_LOCK_PUT_OBJ operation are released; those acquired in
84
operations appearing after the DB_LOCK_PUT_OBJ operation are
86
<p><dt><a name="DB_LOCK_TIMEOUT">DB_LOCK_TIMEOUT</a><dd>Cause the specified <b>locker</b> to timeout immediately. If the
87
database environment has not configured automatic deadlock detection,
88
the transaction will timeout the next time deadlock detection is
89
performed. As transactions acquire locks on behalf of a single locker
90
ID, timing out the locker ID associated with a transaction will time
91
out the transaction itself.
93
<p><dt>DB_LOCK <a name="lock">lock</a>;<dd>A lock reference.
94
<p><dt>const lockmode_t <a name="mode">mode</a>;<dd>The lock mode, used as an index into the environment's lock conflict matrix.
95
When using the default lock conflict matrix, <b>mode</b> must be set to one
96
of the following values:
98
<dt><a name="DB_LOCK_READ">DB_LOCK_READ</a><dd>read (shared)
99
<dt><a name="DB_LOCK_WRITE">DB_LOCK_WRITE</a><dd>write (exclusive)
100
<dt><a name="DB_LOCK_IWRITE">DB_LOCK_IWRITE</a><dd>intention to write (shared)
101
<dt><a name="DB_LOCK_IREAD">DB_LOCK_IREAD</a><dd>intention to read (shared)
102
<dt><a name="DB_LOCK_IWR">DB_LOCK_IWR</a><dd>intention to read and write (shared)
104
<p>See <a href="../api_cxx/env_set_lk_conflicts.html">DbEnv::set_lk_conflicts</a> and <a href="../ref/lock/stdmode.html">Standard Lock Modes</a> for more information on the lock conflict matrix.
105
<p><dt>const Dbt <a name="obj">obj</a>;<dd>An untyped byte string that specifies the object to be locked or
106
released. Applications using the locking subsystem directly while also
107
doing locking via the Berkeley DB access methods must take care not to
108
inadvertently lock objects that happen to be equal to the unique file
109
IDs used to lock files. See <a href="../ref/lock/am_conv.html">Access
110
method locking conventions</a> for more information.
111
<p><dt>u_int32_t timeout;<dd>The lock timeout value.
113
<p>The <b>nlist</b> argument specifies the number of elements in the
115
<p>If any of the requested locks cannot be acquired, or any of the locks to
116
be released cannot be released, the operations before the failing
117
operation are guaranteed to have completed successfully, and
118
DbEnv::lock_vec returns a non-zero value. In addition, if <b>elistp</b>
119
is not NULL, it is set to point to the DB_LOCKREQ entry that was being
120
processed when the error occurred.
122
Otherwise, the DbEnv::lock_vec method either returns a non-zero error value or throws an exception that
123
encapsulates a non-zero error value on failure, and returns 0 on success.
125
<p>The DbEnv::lock_vec method may fail and throw an exception or return a non-zero error for the following conditions:
127
<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
130
<p><dt>ENOMEM<dd>The maximum number of locks has been reached.
132
<p>If the operation was selected to resolve a deadlock, the
133
DbEnv::lock_vec method will fail and
134
and either return <a href="../ref/program/errorret.html#DB_LOCK_DEADLOCK">DB_LOCK_DEADLOCK</a> or
135
throw a <a href="../api_cxx/deadlock_class.html">DbDeadlockException</a> exception.
136
<p>The DbEnv::lock_vec method may fail and throw an exception or return a non-zero error for errors specified for other Berkeley DB and C library or system methods.
137
If a catastrophic error has occurred, the DbEnv::lock_vec method may fail and
138
either return <a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a> or throw a
139
<a href="../api_cxx/runrec_class.html">DbRunRecoveryException</a>,
140
in which case all subsequent Berkeley DB calls will fail in the same way.
142
<a href="../api_cxx/env_class.html">DbEnv</a>, <a href="../api_cxx/lock_class.html">DbLock</a>
144
<a href="../api_cxx/lock_list.html">Locking Subsystem and Related Methods</a>
146
<table width="100%"><tr><td><br></td><td align=right>
147
<a href="../api_cxx/c_index.html"><img src="../images/api.gif" alt="API"></a><a href="../reftoc.html"><img src="../images/ref.gif" alt="Ref"></a>
149
<p><font size=1><a href="http://www.sleepycat.com">Copyright Sleepycat Software</a></font>