Korriban, the starting planet of Sith Inquisitors and Sith Warriors, has 3 Datacrons, all of them very easy to aquire. Read the guide below if you wish to learn quickly how to get them.
Codex Entry - Galactic History 15: Mandalore
Coordinates: 153, 89
The first Datacron can be found in the Valley of the Dark Lords. Follow the eastern road from the shuttle and look for a platform on the right side of the path. Step on it and behind the wall on it's right you will see the Datacron glowing.
Codex Entry - Galactic History 16: The Alsakan Conflicts
Coordinates: 529, 68
The Willpower Datacron is very easy to get to. Go to the Lower Wilds following the main road that starts at the shuttle. Go all the way around the hill and take the right secondary path. At it's end you will see the Datacron glowing.
Red Matrix Shard
Codex Entry - Galactic History 17: The Duinuogwuin Contention
Coordinates: -54, 379
Go to the Valley of The Dark Lords, enter the Tomb of Tulak Hord , cross the Antechamber and you will arrive into an open area ( The Ruined Atrium). The Datacron is located at the the specified coordinates (second image to see location on map).