First, what does this command
omnidbutil -purge -dcbf
actually do?
"The -dcbf option removes DCBF for all media with expired catalog protection."
The DCBF (Detail Catalog Binary File) is the heart of IDB, each file contains all the information for data backed up per media. The 'catalog' is the list of the files and directories on that media, and this is what enables you to restore. Other information in the DCBF identifies the media being used. it is possible to lose teh Catalog, but still import the media to get it back
Unfortunately, since this command was run "omnidbutil -purge -dcbf" it took the entire DCBF with it. That's why you are seeing the blue ? marks
Now, this should only be the case for unprotected media. If this took protected sessions (of course, now, we'll never know), then DP has a real issue
I would recommend a physical scan of a simgle media, by right-clicking on it, and picking Scan. This will load the media, read the header file, and, hopefully update the IDB to some of the session information. This is much more complete than a BarCode scan
It may also come back and say that the media is 'Data Protector Foreign', which means that the Scan recognizes that this is DP formatted media, but, is not currently in the IDB, and, I think, this is the more likely scenario. All you can do from this point is to IMport the media to start Rebuilding the IDB. It will take a log time, it takes LTO-4 tape 3-4 hours to import
Now, the silver lining. If you have been regularly backing up the IDB onto tape, especially with DP 7 and below, you can restore the IDB from the last good backup. Of course, this is based on knowing what tape the IDB backup was done on. if you don't know, and if the IDB backup was in its own backup specification, thre is a file named 'media.log' (you don't say what version of DP you are running or the Cell Manager OS-type, so I can't be more specific) which will tell you wht media the IDB backup was done on