We are on SAS 9.4 M7 on Linux servers. I just recently completed the upgrade to 9.4 M7 from M5. Now If I want to go back to M5, can I just restore /opt/sas (on all 3 tiers - meta, compute and mid) and restart services? Will I be able to go back to M5 version?
Yes, that's right with a condition that integrity of the backup version for /opt/sas is good and cold backup was performed when no file or process was in use.
Also, if you revert back, start the SAS services and users update any content in the older version, you will loose all that as you have already upgraded the system to M7. It's not recommended unless there is something you are trying to fix using this approach.
Thank you @Anand_V for the response. Actually my IT guy and I wanted to test the integrity of the /opt/sas/ backup that he takes before upgrades. I need to upgrade the production SAS and nervous in case something goes wrong. So wanted to do this (restore) exercise on test machine (which is already upgraded to M7) and see if we are able to go back to M5.