Put all readonly tablespaces in read write mode

Recompile all invalid objects

Set the compatible parameter to 12.1.0.1

Gather dictionary statistics

Empty all user recycle bins

An extent contains data blocks that are always physically contiguous on disk.

An extent can span multiple segments.

Each data block always corresponds to one operating system block.

It is possible to have tablespaces of different block sizes.

A data block is the smallest unit of I/O in data files.

It executes successfully and creates an UNDO tablespace in HR_PDB.

It falls and reports an error because there can be only one undo tablespace in a CDB.

It fails and reports an error because the CONTAINER=ALL clause is not specified in the command.

It fails and reports an error because the CONTAINER=CURRENT clause is not specified in the command.

It executes successfully but neither tablespace nor the data file is created.