Todo list this feature is currently unimplemented. the relocation function is called whenever it is necessary to move the data of an item to a different position in the database (e.g. through tree balancing operations, shifts as a result of adds or deletes, etc.). it is intended to allow address/position-dependent data items to be stored in a database in an environment opened with the mdb_fixedmap option. currently the relocation feature is unimplemented and setting this function has no effect. parameters: txn a transaction handle returned by mdb_txn_begin() dbi a database handle returned by mdb_dbi_open() rel a mdb_rel_func function returns: a non-zero error value on failure and 0 on success. some possible errors are: