C: Step 1:
Run the following command to check if there are other offline disks
CellCLI> LIST GRIDDISK ATTRIBUTES name WHERE asmdeactivationoutcome != 'Yes'
If any grid disks are returned, then it is not safe to take the storage server offline because proper Oracle ASM disk group redundancy will not be intact.
E: Step 2:
Inactivate all the grid disks when Oracle Exadata Storage Server is safe to take offline using the following command:
CellCLI> ALTER GRIDDISK ALL INACTIVE
Taking the storage server offline when one or more grid disks are in this state will cause
Oracle ASM to dismount the affected disk group, causing the databases to shut down abruptly.

Oracle Exadata Deployment Assistant has two main phases
Oracle Exadata Deployment Assistant can configure Oracle Exadata Database Machine,
Recovery Appliance, or Oracle SuperCluster.
References:
https://docs.oracle.com/cd/E55822_01/AMOGD/configurator.htm#AMOGD22056
https://www.toadworld.com/platforms/oracle/w/wiki/11469.oracle-exadata-deployment-assistance-oeda

Transportable database approach (TDB). If the source system is running Oracle 11.2 or above with Little Endian format, this method can be used to migrate the database to Exadata.
References:
https://www.toadworld.com/platforms/oracle/w/wiki/11551.managing-troubleshooting-exadata-part-3-migrating-databases-to-exadata-database-machine-best-practices

Whether you get a direct path read & smart scan, depends on the current buffer cache size, how big segment you're about to scan and how much of that segment is actually cached at the moment. This dynamic decision unfortunately can cause unexpected surprises and variance in your report/batch job runtimes.
To work around these problems and force a direct path read/smart scan, you can either:
D: One of the most common Exadata performance problems is that the direct path reads (and thus also Smart Scans) don't sometimes kick in when running full scans in serial sessions.
Note: Smart Scan is a subset of Cell Offload Processing and is perhaps the feature that is most highly associated with Exadata. Smart Scan allows Oracle databases to push query information down to the storage level, specifically: