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

According to Oracle.com documents or resources, the four actions that you should take before proceeding with applying updates to your Exadata Database Machine are:
1. Consult My Oracle Support note 888828.1 to determine the current recommended Exadata software release123.
2. Check the Exadata Critical Issues My Oracle Support note 1270094.1 for any issues not added to the latest version of exachk453.
3. Run exachk and resolve only WARNINGS that you have not seen before3.
4. Run the appropriate patchmgr preqequisite check step for each component being updated3.

According to Oracle's documentation1, the client network on Exadata X9M-2 Database Server is used for client access to the database servers using Single Client Access Name (SCAN) and Oracle RAC Virtual IP (VIP) addresses. To verify that the client network is available via both client switches, you can use the command:
cat /proc/net/bonding/bondeth0
This command displays information about the bondeth0 interface, which is used for the client network on Exadata X9M-2 Database Server2. You can check if both interfaces (eth0 and eth1) are active and connected to different switches3.

It collects configuration information automatically (B). OCM gathers detailed configuration information about a variety of designated Oracle products and components across an enterprise on a regular basis2.
It collects configuration information on demand . OCM can also collect configuration information manually when requested by the user or by Oracle Support2.
Collected configuration information can be uploaded automatically to Oracle (E). OCM can upload the collected configuration information to My Oracle Support automatically for analysis and support purposes3.