Berkeley DB: DbEnv::set_lk_partitions
Description: Berkeley DB: An embedded database programmatic toolkit.
Keywords: embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++

DbEnv::set_lk_partitions |

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    #include <db_cxx.h>

    int
    DbEnv::set_lk_partitions(u_int32_t partitions);

    int
    DbEnv::get_lk_partitions(u_int32_t *lk_partitions);

Description: DbEnv::set_lk_partitions

Set the number of lock table partitions in the Berkeley DB environment. The default value is 10 times the number of CPUs on the system if there is more than one CPU. Increasing the number of partitions can provide for greater throughput on a system with multiple CPUs and more than one thread contending for the lock manager. On single processor systems more than one partition may increase the overhead of the lock manager. Systems often report threading contexts as CPUs this may require setting the number of partitions to 1 to get optimal performance.

The database environment's number of partitions may also be configured using the environment's DB_CONFIG file. The syntax of the entry in that file is a single line with the string "set_lk_partitions", one or more whitespace characters, and the number of partitions. 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_lk_partitions method configures a database environment, not only operations performed using the specified DbEnv handle.

The DbEnv::set_lk_partitions 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_lk_partitions will be ignored.

The DbEnv::set_lk_partitions 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
partitions

- The partitions parameter is the number of partitions to be configured in the Berkeley DB environment.

Errors

The DbEnv::set_lk_partitions 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_lk_partitions

The DbEnv::get_lk_partitions method returns the number of partitions.

The DbEnv::get_lk_partitions method may be called at any time during the life of the application.

The DbEnv::get_lk_partitions 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
lk_partitions

- The DbEnv::get_lk_partitions method returns the number of partitions in lk_partitions.

Class DbEnv, DbLock
See Also Locking Subsystem and Related Methods`

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