int DB_ENV->lock_id(DB_ENV *env, u_int32_t *idp);
The DB_ENV->lock_id method copies a locker ID, which is guaranteed to be unique in the specified lock table, into the memory location to which idp refers.
The DB_ENV->lock_id_free method should be called to return the locker ID to the Berkeley DB library when it is no longer needed.
The DB_ENV->lock_id method returns a non-zero error value on failure and 0 on success.
The DB_ENV->lock_id method may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions. If a catastrophic error has occurred, the DB_ENV->lock_id method may fail and return DB_RUNRECOVERY, in which case all subsequent Berkeley DB calls will fail in the same way.
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