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<h1>DB_ENV->set_tx_max</h1>
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<h3><pre>
#include <db.h>
<p>
int
DB_ENV->set_tx_max(DB_ENV *dbenv, u_int32_t tx_max);
</pre></h3>
<h1>Description</h1>
<p>Set the maximum number of active transactions that are supported by the
environment. This value bounds the size of backing shared memory regions.
Note that child transactions must be counted as active until their
ultimate parent commits or aborts.
<p>When there are more than the specified number of concurrent transactions,
calls to <a href="../api_c/txn_begin.html">DB_ENV->txn_begin</a> will fail (until some active transactions
complete). If no value is specified, a default value of 20 is used.
<p>The DB_ENV->set_tx_max method configures a database environment, not only operations
performed using the specified <a href="../api_c/env_class.html">DB_ENV</a> handle.
<p>The DB_ENV->set_tx_max interface may not be called after the <a href="../api_c/env_open.html">DB_ENV->open</a>
interface is called.
If the database environment already exists when
<a href="../api_c/env_open.html">DB_ENV->open</a> is called, the information specified to DB_ENV->set_tx_max
will be ignored.
<p>The DB_ENV->set_tx_max method returns a non-zero error value on failure and 0 on success.
<p>The database environment's maximum number of active transactions may also be set using the environment's
<b>DB_CONFIG</b> file. The syntax of the entry in that file is a
single line with the string "set_tx_max", one or more whitespace characters,
and the number of transactions. Because the <b>DB_CONFIG</b> file is read when the database
environment is opened, it will silently overrule configuration done
before that time.
<h1>Errors</h1>
<p>The DB_ENV->set_tx_max method may fail and return a non-zero error for the following conditions:
<p><dl compact>
<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
<p>Called after <a href="../api_c/env_open.html">DB_ENV->open</a> was called.
</dl>
<p>The DB_ENV->set_tx_max method may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions.
If a catastrophic error has occurred, the DB_ENV->set_tx_max method may fail and
return <a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a>,
in which case all subsequent Berkeley DB calls will fail in the same way.
<h1>Class</h1>
<a href="../api_c/env_class.html">DB_ENV</a>, <a href="../api_c/txn_class.html">DB_TXN</a>
<h1>See Also</h1>
<a href="../api_c/txn_list.html">Transaction Subsystem and Related Methods</a>
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