Explanation
The Oracle Cloud Infrastructure Compute service provides console connections that enable you to remotely troubleshoot malfunctioning instances, such as:
An imported or customized image that does not complete a successful boot.
A previously working instance that stops responding.
the steps to connect to console and troubleshoot the OS Issue
1- Before you can connect to the serial console you need to create the instance console connection.
Open the navigation menu. Under Core Infrastructure, go to Compute and click Instances.
Click the instance that you're interested in.
Under Resources, click Console Connections.
Click Create Console Connection.
Upload the public key (.pub) portion for the SSH key. You can browse to a public key file on your computer or paste your public key into the text box.
Click Create Console Connection.
When the console connection has been created and is available, the status changes to ACTIVE.
2- Connecting to the Serial Console
you can connect to the serial console by using a Secure Shell (SSH) connection to the service endpoint of the console connection service Open the navigation menu. Under and click Instances.
Click the instance that you're interested in.
Under Resources, click Console Connections
Click the Actions icon (three dots), and then click Copy Serial Console Connection for Linux/Mac.
Paste the connection string copied from the previous step to a terminal window on a Mac OS X or Linux system, and then press Enter to connect to the console.
If you are not using the default SSH key or ssh-agent, you can modify the serial console connection string to include the identity file flag, -i , to specify the SSH key to use. You must specify this for both the SSH connection and the SSH ProxyCommand, as shown in the following line:
ssh -i /<path>/<ssh_key> -o ProxyCommand='ssh -i /<path>/<ssh_key> -W %h:%p -p 443...
Press Enter again to activate the console.
3- Troubleshooting Instances from Instance Console Connections
To boot into maintenance mode
Reboot the instance from the Console.
When the reboot process starts, switch back to the terminal window, and you see Console messages start to appear in the window. As soon as you see the GRUB boot menu appear, use the up/down arrow key to stop the automatic boot process, enabling you to use the boot menu.
In the boot menu, highlight the top item in the menu, and type e to edit the boot entry.
In edit mode, use the down arrow key to scroll down through the entries until you reach the line that starts with either linuxefi for instances running Oracle Autonomous Linux 7.x or Oracle Linux 7.x, or kernel for instances running Oracle Linux 6.x.
At the end of that line, add the following:
init=/bin/bash
Reboot the instance from the terminal window by entering the keyboard shortcut CTRL+X.

Real-time processing of high-volume streams of data
- OCI Streaming service provides a fully managed, scalable, durable storage option for continuous, highvolume streams of data that you can consume and process in real-time
- Use cases
Log and Event data collection
Web/Mobile activity data ingestion
IoT Data streaming for processing and alerts
Messaging: use streaming to decouple components of large systems
- Oracle managed service with REST APIs (Create, Put, Get, Delete)
- Integrated Monitoring

Explanation
A 503 Service Unavailable Error is an HTTP response status code indicating that a server is temporarily unable to handle the request. This may be due to the server being overloaded or down for maintenance.

There's an advanced routing scenario called transit routing that enables communication between an onpremises network and multiple VCNs over a single Oracle Cloud Infrastructure FastConnect or IPSec VPN.
The VCNs must be in the same region and locally peered in a hub-and-spoke layout. As part of the scenario, the VCN that is acting as the hub has a route table associated with each LPG (typically route tables are associated with a VCN's subnets).