Berkeley DB: DbEnv::set_thread_count
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_thread_count |

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    #include <db_cxx.h>

    int
    DbEnv::set_thread_count(u_int32_t count);

    int
    DbEnv::get_thread_count(u_int32_t *countp);

Description: DbEnv::set_thread_count

Declare an approximate number of threads in the database environment. The DbEnv::set_thread_count method must be called prior to opening the database environment if the DbEnv::failchk method will be used. The DbEnv::set_thread_count method does not set the maximum number of threads but is used to determine memory sizing and the thread control block reclamation policy.

If a process has not configured an is_alive function from the DbEnv::set_isalive method, and then attempts to join a database environment configured for failure checking with the DbEnv::failchk, DbEnv::set_thread_id, DbEnv::set_isalive and DbEnv::set_thread_count methods, the program may be unable to allocate a thread control block and fail to join the environment. This is true of the standalone Berkeley DB utility programs. To avoid problems when using the standalone Berkeley DB utility programs with environments configured for failure checking, incorporate the utility's functionality directly in the application, or call the DbEnv::failchk method before running the utility.

The database environment's thread count 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_thread_count", one or more whitespace characters, and the thread count. 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_thread_count method configures operations performed using the specified DbEnv handle, not all operations performed on the underlying database environment.

The DbEnv::set_thread_count method may not be called after the DbEnv::open method is called.

The DbEnv::set_thread_count 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
count

- The count parameter is an approximate thread count for the database environment.

Errors

The DbEnv::set_thread_count 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_thread_count

The DbEnv::get_thread_count method returns the thread count.

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

The DbEnv::get_thread_count 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
countp

- The DbEnv::get_thread_count method returns the thread count in countp.

Class DbEnv
See Also Database Environments and Related Methods`

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