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DbEnv::set_tx_max
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#include &lt;db_cxx.h&gt;

int
DbEnv::set_tx_max(u_int32_t max);

int
DbEnv::get_tx_max(u_int32_t *tx_maxp);
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Description: DbEnv::set_tx_max
Configure the Berkeley DB database environment to support at least max
active transactions. This value bounds the size of the memory allocated
for transactions. Child transactions are counted as active until they
either commit or abort.
Transactions that update multiversion databases are not freed until the
last page version that the transaction created is flushed from cache.
This means that applications using multi-version concurrency control may
need a transaction for each page in cache, in the extreme case.
When all of the memory available in the database environment for
transactions is in use, calls to <a href="../../db4-devel-4.7.25/api_cxx/txn_begin.html">DbEnv::txn_begin</a> will fail (until some
active transactions complete). If this interface is never called, the
database environment is configured to support at least 100 active
transactions.
The database environment's number of active transactions may also be configured using the
environment's <a href="../../db4-devel-4.7.25/ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> 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 <a href="../../db4-devel-4.7.25/ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file is read when the database environment
is opened, it will silently overrule configuration done before that
time.
The DbEnv::set_tx_max method configures a database environment, not only operations
performed using the specified <a href="../../db4-devel-4.7.25/api_cxx/env_class.html">DbEnv</a> handle.
The DbEnv::set_tx_max method may not be called after the <a href="../../db4-devel-4.7.25/api_cxx/env_open.html">DbEnv::open</a> method is
called.
If the database environment already exists when
<a href="../../db4-devel-4.7.25/api_cxx/env_open.html">DbEnv::open</a> is called, the information specified to DbEnv::set_tx_max
will be ignored.

The DbEnv::set_tx_max method
either returns a non-zero error value
or throws an exception that encapsulates a non-zero error value on
failure, and returns 0 on success.

Parameters 
 max<ul compact><li>The max parameter configures the minimum number of
simultaneously active transactions supported by Berkeley DB database
environment.</ul>
 
 Errors
The DbEnv::set_tx_max method
may fail and throw
<a href="../../db4-devel-4.7.25/api_cxx/except_class.html">DbException</a>,
encapsulating one of the following non-zero errors, or return one of
the following non-zero errors:
 
EINVAL<ul compact><li>If the method was called after <a href="../../db4-devel-4.7.25/api_cxx/env_open.html">DbEnv::open</a> was called; or if an
invalid flag value or parameter was specified.</ul>
 
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Description: DbEnv::get_tx_max
The DbEnv::get_tx_max method returns the number of active transactions.
The DbEnv::get_tx_max method may be called at any time during the life of the
application.
The DbEnv::get_tx_max method
either returns a non-zero error value
or throws an exception that encapsulates a non-zero error value on
failure, and returns 0 on success.

Parameters 
 tx_maxp<ul compact><li>The DbEnv::get_tx_max method returns the
number of active transactions in tx_maxp.</ul>
 
<hr size=1 noshade>
 Class
<a href="../../db4-devel-4.7.25/api_cxx/env_class.html">DbEnv</a>, <a href="../../db4-devel-4.7.25/api_cxx/txn_class.html">DbTxn</a>
 See Also
<a href="../../db4-devel-4.7.25/api_cxx/txn_list.html">Transaction Subsystem and Related Methods</a>
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