How I solved Unable to open Oracle Database, EM 404

Upon checking our Enterprise Manager for a daily check to see that everything is okay, backups run successfully etc, I see an error 404 page not found.

I ssh-ed into the server, and tried to connect to the database.

I got the “Connected to idle instance.”

So i tried mounting the DB- no problem.

Next step was to open it- And that’s where it failed.

“ORA-03113: end-of-file on communication channel”

So I checked the alert log, and saw that there were lots of “Disk I/O” errors.

Checked the free space with df -h , and saw that the filesystem used for archive logs was 100% full.

Went into the archive logs folder and used this nifty command to list the 10 largest folders/files,

du -shx * | sort -rh | head -10

and then deleted the largest older folder, freeing up 2.7 GB.

Went back to sqlplus, startup open, and voila - Success.

Went back into the EM, and it said “Backend WLS or EM seems to be down”.

Waited a few minutes, tried again, and logged in with no further trouble.

If you the EM doesn’t start itself like it did for me, you can check out tthis useful page:

http://lefterhs.blogspot.co.il/2012/02/backend-wls-or-em-application-seems-to.html