Berkeley DB: DbEnv::set_mp_max_write
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_mp_max_write |

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    #include <db_cxx.h>

    int
    DbEnv::set_mp_max_write(int maxwrite, db_timeout_t maxwrite_sleep);

    int
    DbEnv::get_mp_max_write(int *maxwritep, db_timeout_t *maxwrite_sleepp);

Description: DbEnv::set_mp_max_write

The DbEnv::set_mp_max_write method limits the number of sequential write operations scheduled by the library when flushing dirty pages from the cache.

The database environment's maximum number of sequential write operations 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_mp_max_write", one or more whitespace characters, and the maximum number of sequential writes and the number of microseconds to sleep, also separated by whitespace characters. 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_mp_max_write method configures a database environment, not only operations performed using the specified DbEnv handle.

The DbEnv::set_mp_max_write 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
maxwrite

- The maximum number of sequential write operations scheduled by the library when flushing dirty pages from the cache, or 0 if there is no limitation on the number of sequential write operations.

maxwrite_sleep

- The number of microseconds the thread of control should pause before scheduling further write operations. It must be specified as an unsigned 32-bit number of microseconds, limiting the maximum pause to roughly 71 minutes.

Errors

The DbEnv::set_mp_max_write method may fail and throw DbException, encapsulating one of the following non-zero errors, or return one of the following non-zero errors:

EINVAL

- An invalid flag value or parameter was specified.

Description: DbEnv::get_mp_max_write

The DbEnv::get_mp_max_write method returns the current maximum number of sequential write operations and microseconds to pause.

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

The DbEnv::get_mp_max_write 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
maxwritep

- The maxwritep parameter references memory into which the maximum number of sequential write operations is copied.

maxwrite_sleepp

- The maxwrite_sleepp parameter references memory into which the microseconds to pause before scheduling further write operations is copied.

Class DbEnv, DbMpoolFile
See Also Memory Pools and Related Methods`

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