Oracle Database supports different techniques for detecting, repairing, and
monitoring block corruption. The technique depends on whether the corruption is interblock
corruption or intrablock corruption. In intrablock corruption, the corruption occurs within the
block itself. This corruption can be either physical or logical. In an interblock corruption, the
corruption occurs between blocks and can only be logical.
Note:
*The main purpose of RMAN validation is to check for corrupt blocks and missing files. You
can also use RMAN to determine whether backups can be restored. You can use the
following RMAN commands to perform validation:
VALIDATE
BACKUP ... VALIDATE
RESTORE ... VALIDATE

* The CREATE DATABASE ... ENABLE PLUGGABLE DATABASE SQL statement creates a new CDB. If you do not specify the ENABLE PLUGGABLE DATABASE clause, then the newly created database is a non-CDB and can never contain PDBs.
Along with the root (CDB$ROOT), Oracle Database automatically creates a seed PDB (PDB$SEED). The following graphic shows a newly created CDB: * Creating a PDB Rather than constructing the data dictionary tables that define an empty PDB from scratch, and then populating its Obj$ and Dependency$ tables, the empty PDB is created when the CDB is created. (Here, we use empty to mean containing no customer-created artifacts.) It is referred to as the seed PDB and has the name PDB$Seed. Every CDB non-negotiably contains a seed PDB; it is non-negotiably always open in read-only mode. This has no conceptual significance; rather, it is just an optimization device. The create PDB operation is implemented as a special case of the clone PDB operation.