#include <db_cxx.h> int DbSequence::open(DbTxn *txnid, Dbt *key, u_int32_t flags);
         The DbSequence::open() method opens the sequence represented by the
         key. The key must be compatible with
         the underlying database specified in the corresponding call to 
         DbSequence.
    
         The DbSequence::open() 
            
            
                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 flags parameter must be set to 0 or by bitwise inclusively OR'ing together one or more of the following values:
                  DB_CREATE
            
                 Create the sequence.  If the sequence does not already exist and the
                 DB_CREATE flag is not specified, the 
                 DbSequence::open() method will fail.
            
                 DB_EXCL
            
                 Return an error if the sequence already exists.  This  flag is only
                 meaningful when specified with the DB_CREATE  flag.
            
                 Cause the DbSequence 
                 handle returned by DbSequence::open() to be
                 free-threaded; that is, usable by multiple
                 threads within a single address space.  Note that if multiple threads
                 create multiple sequences using the same database handle that handle
                 must have been opened specifying this flag.
            
If the operation is part of an application-specified transaction, the txnid parameter is a transaction handle returned from DbEnv::txn_begin(); if the operation is part of a Berkeley DB Concurrent Data Store group, the txnid parameter is a handle returned from DbEnv::cdsgroup_begin(); otherwise NULL. If no transaction handle is specified, but the operation occurs in a transactional database, the operation will be implicitly transaction protected. Transactionally protected operations on a DbSequence handle require the DbSequence handle itself be transactionally protected during its open if the open creates the sequence.