CA PPM Upgrade is heavy on transactions and it's not unusual to have significant transaction log growth for large customers. This means there is that much transactions that were done, a lot of rows and updates, uncommitted updates and such.
Unfortunately there is nothing we can do directly in the CA PPM application as the upgrade process does not do backups and this is why we have to get the process to finish
Here is what we recommend to be done in these cases:
1. Make sure the recovery is set to simple for the upgrade 2. Make sure the transaction log is shrank before you start 3. Add additional disk space 4. Upgrade 5. After upgrade finishes you may remove the additional disk space after shrinking the log again, and reset the recovery mode back to full