I create a memory pool with flag(DB_CREATE) after ope a Db_Env with flag(DB_CREATE | DB_INIT_MPOOL |DB_SYSTEM_MEM), when I run their program at first time, it's ok and create some db files such _db.001,_db.002,mpool, but after I close the program and run it again,their make a error said the system cannot find the specified file("Mpool: PANIC:No such file or directory"), if I delete all files in the memory pool folder and run it again it will be ok? How can I fix this problem?