#include <db_cxx.h> int DbEnv::set_thread_count(u_int32_t count);
Declare an approximate number of threads in the database environment. This method allocates resources in your environment for the threads your application will use. If you fail to properly estimate the number of threads your application will use, your application will run out of resources and errors will be returned when the application attempts to start one too many threads.
         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.
    
         The DbEnv::set_thread_count() method must be called 
         prior to opening the database environment. In addition, this method must be
         used with the
         DbEnv::failchk()  method.
    
If a process invokes this method without the use of DbEnv::failchk() the program may be unable to allocate a thread control block. This is true of the standalone Berkeley DB utility programs.
         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.
            
        
    
                         The DbEnv::set_thread_count() 
            
            
                method may fail and throw a DbException 
                exception, encapsulating one of the following non-zero errors, or return one
                of the following non-zero errors:
            
        
                    
If the method was called after DbEnv::open() was called; or if an invalid flag value or parameter was specified.