First planet the Asgard designated they would use to rebuild their civilization after their war with the Replicators, effectively becoming their new homeworld. It is probably located in the galaxy of Othalla. The planet is rich in neutronium, a key element in Asgard technology. Unfortunately it is the primary ingredient in humanoid Replicators, making it an appealing target to any that remain.
Orilla was the first target of the Replicators when they escaped the time dilation field of Halla. Anticipating a counter-attack upon arrival, the humanoid Replicator Fifth transported both himself and Samantha Carter when the cruiser arrived in orbit. The cruiser was obliterated by Aegir and the Valhalla, along with a team of Asgard motherships. But countless Replicator blocks rained down on the colony, not to mention the group that was transported with Fifth.
Only after the completion of a Replicator disruptor was Orilla rid of the Replicator threat. The Ancient knowledge which had unspooled in Jack O'Neill's mind provided the Asgard with a weapon to counteract their enemy's hungry replication, rendering all kerons on the world inert.
New Order, Part 1 - Thor and Carter chase the Replicator cruiser in the hopes that they will reach it before it arrives at Orilla.
New Order, Part 2 - Thor transports SG-1 to the surface of Orilla to buy him time as he completes the designs for the planet-scale Replicator disruptor.
Unending - Unable to solve their genetic degradation problem, the Asgard commit mass suicide by destroying the planet Orilla.