Needless to say, this should not happen, so I hope you have the data on that volume backed up.
You have to run vrepair.nlm on the server console. I don't recommend doing this when the server is in use as it is resource intensive. Also dismount VOL1 and VOL3 to free up their resources.
At the server prompt on the console, type: load vrepair
If vrepair is available it will bring up a small menu with options 1 - repair a volume
2 - set vrepair options
0 - exit
First of all check the vrepair options and ensure write only changed FAT and directory entries is set and also keep all changes in memory for later writing is set.
Then return to the main menu and select option 1. Only dismounted volumes can be repaired, so your volume should be a candidate. If it isn't there then something catastrophic has happened, and you will need to rebuild the volume because vrepair does not see it.
If vrepair runs, it will analyze the volume and log the errors it finds. When done, it will give you the option to write the changes to the volume. If there are a large number of errors the process will exhaust memory and vrepair will either fail or ask to write changes to disk. If that occurs it is an indication the situation is serious and if data is not currently backed up you should reconsider your options.
If vrepair succeeds, try mounting the volume. If that works then dismount it again and run vrepair again to see if there are new errors. Iterate until clean. Then mount the volume and get a current backup of the data. Then mount the other volumes and put the server back in service.
Good luck.
Jock
