Run-Time Abstraction Services (RTAS) is run-time firmware that provides abstraction to some operating systems. These include those running on IBM System i and IBM System p computers.
It contrasts with Open Firmware, in that the latter is usually used only during boot, while RTAS is used during run-time.
Later it was renamed to Open Power Abstraction Layer (OPAL), and it's stored in a PNOR (platform NOR) flash memory.
Ppc64-diag, libservicelog, servicelog, and powerpc-utils packages can be used to diagnose RTAS events.
References
PowerPC Microprocessor Common Hardware Reference Platform. s.l.: Elsevier. 2012-06-25. ISBN 978-0-12-801555-1. 978-0-12-801555-1 ↩
"Linux on IBM Systems". IBM. 2023-05-10. Retrieved 2025-07-07. https://www.ibm.com/docs/no/linux-on-systems?topic=tools-diagnosing-rtas-events ↩