According to the Oracle documentation1, two statements that are true about enabling write-back flash cache are:
Write-back flash cache is on by default for High Capacity Storage Servers in High Redundancy configurations (A). This is because write-back flash cache provides better performance and reliability for data file writes than write-through flash cache.
Before write-back flash cache is enabled, you need to drop the Flash Cache first (D). This is because changing the flash cache mode requires recreating the flash cache with a different configuration.

According to Oracle's documentation1, to set a threshold for a metric on a database server, you need to use the create threshold command with the appropriate parameters. The set threshold command is used to modify an existing threshold2.
Therefore, the command that you should use to generate alerts for such an event is:
dbmcli -e "create threshold ds_temp comparison='>', critical=30" on each database server1

Exadata Secure RDMA Fabric isolation is a feature that allows you to use virtualization on the X9M-2 platform while maintaining security and isolation between multiple tenants or VM clusters. Secure Fabric isolation works by creating a dedicated network partition and VLAN ID for each Database VM cluster, which is used for cluster networking between the database servers in the VM Cluster. This ensures that the network traffic of each VM cluster is isolated from the others, and it prevents unauthorized access to the data or resources of other VM clusters. Secure Fabric isolation can also be used for other purposes such as client networking, Data Guard traffic, but it's mainly used to provide security and isolation between multiple tenants or VM clusters.
According to Oracle's documentation1, Exadata Secure RDMA Fabric Isolation is a feature that enables strict network isolation for Oracle Real Application Clusters (Oracle RAC) clusters on Exadata Database Machine systems that use RDMA over Converged Ethernet (RoCE). Exadata Secure RDMA Fabric Isolation uses RoCE VLANs to ensure that network packets from one VM cluster cannot be seen by another VM cluster. VLAN tag enforcement is done at the KVM host level, which means that security cannot be bypassed by any software exploits or misconfiguration on the database server VMs1.
Therefore, the statement that is true about how Exadata Secure RDMA Fabric isolation is used in X9M-2 with virtualization enabled is:
With Secure Fabric isolation, each Database VM cluster uses a dedicated network partition and VLAN ID for cluster networking between the database servers in the VM Cluster. This provides security and isolation between multiple tenants or VM clusters.

A) YOU query VSSYSTEM_EVENTS and filter for the event 'cell physical IO interconnect bytes returned by smart scan', associated to your table. This does not show how much data was filtered by Smart Scan, but only how much data was returned after Smart Scan12.
C) You query v$SYSTAT and filter for the statistic 'cell smart table scan', associated to your table. This does not show how much data was filtered by Smart Scan for a specific table, but only for all tables in a session12.
https://www.databasejournal.com/oracle/monitoring-smart-scans-in-oracle-exadata/

According to the Oracle Exadata Database Machine documentation12, two recommended configuration best practices for backup and recovery on Exadata are:
A) Placing the backup network on dedicated switches installed in the top of the rack (ToR) has the benefits of isolating the backup network from other workloads and providing a greater level of control.
D) When off-site long-term backup retention is needed, use Oracle Database Backup Cloud Service as a low-cost, offsite scalable storage for a disaster recovery solution.