Exadata Dom0 and DomU.

An Exadata Database Server contains at least one Virtual Machine (VM), known as DomU, running on a VM hypervisor or virtual machine monitor (VMM), known as Dom0.

Dom0:  Dom0 can only be accessed by the Oracle Team. The resource allocated to Dom0 is minimal. It runs on 2 CPUs and 16GB RAM. Oracle uses the Integrated Lights Out Manager (ILOM) which is a highly specialized tool created to manage and monitor servers. ILOM controls the hardware and firmware of the Dom0 Database Server.

DomU :  Users have secure access to DomU. Each DomU is provisioned with a complete Oracle Database installation including all the features of Oracle Database Enterprise Edition, Oracle Grid Infrastructure with Cloud Tools. In DomU, the client patches and maintains the operating system, grid, Exadata, etc. 

A hypervisor, also known as a virtual machine monitor or VMM, is software that creates and runs virtual machines (VMs). 

Patching sequence and it will be always rolling.

-  Dom0

-  Cell Server

-  IBswitch

-  DomU

1. Dom0 Patching: 

- Dom0 rolling patching requires 90 minutes to complete the Pre-patching checks, service & pdb reallocation in DomUs, infrastructure patching & configuration updates in dom0, post patching checks and restart all DomUs in Physical (compute) node.

- Full Rack Exadata (KVM) Server contains maximum 8 DomUs in each physical (compute) node. (Elastic Exadata in OCI - VMs & Cell severs can be extended). 

- For a single Full Rack Exadata Server, total 720 Minutes (90 Minutes*8 compute physical nodes) needed for completing Dom0 patching. 

2. Cell Server Patching: 

      

- Rolling Cell Server Patching will take 30 Minutes to complete the patching (Pre-patching checks, making grid disks offline, Storage patching, making grid disks online etc.) in each Cell Server (Excluding ASM rebalancing effort. Additional 10 Minutes per cell sever needed for an ASM rebalancing activity). 

- Full Rack Exadata Server contains 14 Cell servers. and each Cell server contains 12 Cell (hard) disks.

- For a single Full Rack Exadata Server, total 560 Minutes (40 Minutes*14 cell servers) needed for completing the Cell Server patching. 

3. InfiniBand Switch Patching: 

     

- Exadata KVM Server contains 2 InfiniBand (Rocky) switches (Active & Passive switches).  

- Patching activity will take 15 Minutes to complete the patching in each switch.  

- For a single Full Rack Exadata Server, total 30 Minutes (15 Minutes*2 switches) needed for completing the Switch patches. 

4. DomU Patching: 

- DomU rolling patching requires 40 Minutes to complete the Pre-patching checks, service & pdb reallocation, VM patching & configuration updates in domU, post patching checks and restart all DomUs in Physical (compute) node.  

- Full Rack Exadata (KVM) Server contains maximum 8 DomUs in each physical (compute) node.   

- For a single Full Rack Exadata Server, total 320 Minutes (40 Minutes*8 compute physical nodes) needed for completing the DomU patching.