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Berkeley DB: DbEnv::set_tx_max
DbEnv::set_tx_max
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#include <db_cxx.h>
int
DbEnv::set_tx_max(u_int32_t max);
int
DbEnv::get_tx_max(u_int32_t *tx_maxp);
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.
When all of the memory available in the database environment for
transactions is in use, calls to DbEnv::txn_begin will fail (until some
active transactions complete). If this interface is never called,
the database environment is configured to support at least 20 active
transactions.
The database environment's number of active transactions may also be set using the environment's
DB_CONFIG 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 DB_CONFIG 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 DbEnv handle.
The DbEnv::set_tx_max method may not be called after the DbEnv::open method is
called.
If the database environment already exists when
DbEnv::open 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
- The max parameter configures the minimum number of
simultaneously active transactions supported by Berkeley DB database
environment.
Errors
The DbEnv::set_tx_max method
may fail and throw
DbException,
encapsulating one of the following non-zero errors, or return one of
the following non-zero errors:
- EINVAL
- If the method was called after DbEnv::open was called; or if an
invalid flag value or parameter was specified.
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
- The DbEnv::get_tx_max method returns the
number of active transactions in tx_maxp.
Class
DbEnv, DbTxn
See Also
Transaction Subsystem and Related Methods
Copyright (c) 1996-2004 Sleepycat Software, Inc. - All rights reserved.
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