Technically, going directly from 7.3 to 9.6 is not a supported upgrade/migration path - https://docs.bmc.com/docs/display/public/proactivenet96/Upgrading+BMC+Event+and+Impact+Management+to+BMC+ProactiveNet+Server.
However, to see if you could still make this workout - depending on how you copied the file, the line endings could have changed and caused truncation in the file. You might try zipping it first then copying that.
Also, if you don't want to carry over the service model data/etc and just want the events, you might start the cell once more on the 7.3 system with the -id switch to reinit all data, then have the cell run statbld (mcontrol -n <cellname> statbld), then zip & copy the mcdb. Take a backup of the mcdb first, in case you do not like the results.
To get the events, you would only need the mcdb file, not any of the sm* files.
I just copied the whole mcdb using Windows WinSCP.
Unfortunately I don't see how the staged upgrade can work when we need to basically stop our BEM 7.3 system and copy/migrate the events into the new BPPM environment immediately. The outage window spans multiple hours but it would not be long enough to actually upgrade the software at the same time.
If I fiddle with the headers in mcdb I can get the cell to start and stay up but it doesn't recognize the events or custom data. It just shows up in IX as if I had started the cell with the -ia option.
If I could find out what the header information means (as it is different between 7.3 and 9.6) it might help...
We are also performing Migration BEM 74 to BPPM 96. As part of it, we performed test and we copied MCDB from old environment to BPPM in order to see all events in SIM cell as in BPPM pncell.
After copying MCDB, we had to restart BPPM Server in order to see events on PnCell.
There will not be any issue related to Sync between BPPM - ITSM and old events can be closed even if events are existing on BPPM pncell.
Hope this answers your queries.
Recommedning not to Copy smXXX and daXXX, evXXx files. Leave them as they are in new BPPM Pn Cell.