I have Avast on two different computers. On the first the avast4.db file is about 1.8gb in size. On the second the same file is about 190mb. I’d like to delete the large one and I don’t know if Avast will just rebuild it at a much smaller size, or replace it’s current size…or if doing so will just kill the program (and require re-installation). Can someone give me an idea about handling this?
John
Well mine is 52KB so there is a big difference in even your smallest one. As far as I’m aware this is where all your settings are kept I only have one user account (other than the administrator account) on this system, if you have multiple users and you have made a lot of tweaks I could se that grow but not to those sizes.
How long have you have avast installed on both systems ?
The avast self-defence would block your doing this, so would have to be disabled, program settings, troubleshooting. Or you could boot into safe mode (avast doesn’t run in safe mode) and delete the file from there and reboot into normal mode.
Though I have no idea what the effect might be if you did delete it, e.g. would it screw your avast installation, possibly. I don’t know if avast would simply rebuild it in any integrity check finds it missing or would it just crash, I don’t know, so we will have to wait for some input from one of the Alwil team. You could try it on one system and see what happens be prepared to the the clean reinstall detailed below and have the new version and uninstall utility already downloaded.
Though a safer option would be to do a reinstall - Download the latest version of avast 4.8.1282 http://www.avast.com/eng/download-avast-home.html and save it to your HDD, somewhere you can find it again. Use that when you reinstall.
Download the avast! Uninstall Utility, find it here and save it to your HDD.
This should ensure a complete clean reinstall.
Do you use avast! Professional? (unlike avast! Home)
If it’s avast! Pro, the avast4.db file contains the results of stored sessions (maybe you enabled “OK files” to be stored in the storage? - it can be rather huge then). So, if you start Enhanced User Interface and delete the sessions you no longer need, the file should shrink (but not immediatelly, after some time).
I don’t recommend deleting the file directly (if possible at all) - there are some program settings there (e.g. of the resident protection) and I don’t dare to predict the consequences.
You can also configure how many days should the sessions be kept. avast will automatically drop old sessions informations and reduce the file size 
I’ve done two things. I changed the setting to automatically delete sessions after 2 days. There were 7 sessions saved going back a month. But even after closing and opening the program numerous times, the sessions remained. So I used the delete sessions choice, and one at a time (what a drag…this was my old slow computer) I deleted all but two sessions. But even after numerous more closing and openings of the programs, the avast4.db file remained the same size (189,866,464).
What do you think is necessary to get this file to reflect the smaller number of sessions? And either they are huge session reports, or there’s something else inside this file taking up space.
I also tried to delete the avast4.db file but wasn’t allowed to. I stopped all the Avast services and tried again to delete it, but to no matter. I don’t much care if I loose settings, I tend to use Avast for manual scans only. I can probably boot up in Dos and delete the damn file(or Safe Mode as suggested, but I’m curious why it didn’t change after deleting the sessions, or after changing the number of days sessions are saved for(do I have to wait until after midnight for this to work?).
Thanks for all the suggestions, especially the link to the uninstall program. I’ll see if there’s any change tomorrow.
John
Did you try to restart the “avast! antivirus” service after deleting the sessions?
As with most databases, the file is not shrinked immediately.
BTW in order to delete the file, you must disable the avast self-defense module (avast settings → Troubleshooting page).
Obviously, all the avast components must be closed / shut down prior to doing that.
Thanks
Vlk
Sorry to take so long to get back to this…hope you’re still watching.
I’ve tried disabling the self-defense module and also stopping all the running services. But this didn’t help, I still can’t delete the 186mb avast4.db file. And it is not changing size even though I deleted all the sessions and have rebooted and restarted the program many times since my last message. Any other suggestions, are there some permissions that I can disable, some registry keys???
Maybe booting in Safe Mode and deleting the file within there…