Hi,

We often get this error message and reasons could be various. Below are the various solutions.

Solution1:
In general, ALM restart would fix this issue. Go to the Services and Stop the services and take a while and then start the services. This will resolve the issue.

Solution2:
Please try to clearing the temp files in the QC client cache. type the %temp% in the windows explorer and search. you can see the td_80 folder and you can delete that. And also, you can delete cache in IE as well. Please delete temp folder and make sure you have enough space in the QC server/client machines.

Solution3: If ALM and Database are running in different servers.
ALM server might not be able to communicating with the database server if you running ALM and DB in different servers.

- Ping DB Server from ALM server and vice versa. Make sure both the servers are up and running and able to communicate each other.
- If any issues found during ping. check the error message and work accordingly.
a) Check the internet connectivity in both the machines.
b) Check if ports are blocked. if yes, work with the network team to get it unlock the ports.
- Make sure Database is online and user can login to the ALM database successfully.
- restart the database service in the database server and restart the ALM service in ALM server also.
- restart both the machines and try launching the ALM. It should work.

Solution4: Add a dependency to the ALM service for the MSSQLSERVER. Below article talks about the same.
http://eyeontesting.com/questions/11371/how-do-we-stop-getting-this-http-error-503.html

Solution5: SQL-Server with ''Windows-authentication''
http://eyeontesting.com/questions/8323/our-alm-instance-is-down.html

Solution6:
http://eyeontesting.com/questions/11899/service-unavailable-message-in-browser.html

Solution7: If issue related to mobile center
http://eyeontesting.com/questions/16107/hpmc-down-with-http-503-error.html

I hope, This information will be helpful to resolve the HTTP 503 Error in ALM. Thank you..