Cause:

Error:DB_BLOCK_SIZE must be <num> to mount this database not <num>

Cause: The DB_BLOCK_SIZE parameter value in the initialization parameter file used to start a database does not match the value used when that database was created. Potential reasons for this mismatch are mounting the wrong database using the wrong initialization parameter file the DB_BLOCK_SIZE value was changed

see: Oracle error ORA-00058: DB_BLOCK_SIZE must be <num> to mount this database not <num>