ORA-00058: DB_BLOCK_SIZE must be 16384 to mount this database

This error may be returned during different scenarios; however, the root cause may be the same. I was trying to use duplicate command to build a database from backup of another database that had default block size of 16k. Since 8k is default block size of an Oracle database, we MUST specify db_block_size in the init file of the auxiliary instance to the same block size of the source database we are using to build this new database. After I modified the value of this parameter to 16384 in the init file of the auxiliary instance, error did not appear on second attempt of DUPLICATE database command and I was able to build the new database.

ORA-31655: no data or metadata objects selected for job

 Whenever datapump export is initiated, it should (mainly) either by database level, schema level, or table level. If you omit to tell expdp about the mode of datapump export, ORA-31655 is returned. Therefore, you should always make sure that that you provide level/mode of export datapump whenever you invoke expdp. For example, use parameter full=y for database level export, or schemas parameter for schema level or tables parameter for table level export.