CiviMail DB Error: no database selected

Question

Civi 4.6.15 Joomla 3.5.1

Previously I upgraded my civi version to 4.7, and somehow I corrupted my database. I reinstalled a clean 4.6.15 and restored my database from backup.

It seemed to be working. I was able to send a New Mailing by executing "Send Scheduled Mailings" with no issues. 10 minutes later, I attempted to send another email to the same group and the same manual execution, but I'm getting:

Sorry but we are not able to provide this at the moment.
DB Error: no database selected

Return to home page.

I can still access contacts, and I can still see the groups.

Any ideas on where to start?

-EDIT 5/8/16-

I ended up exporting contact info, uninstalling Civi, deleting the media folder, deleting all associated database info in my Joomla database, reinstalling Civi (4.7.7), and importing contacts back into the system. Yes, it's an insane Neanderthal way to do it, but I ran out of options.

I just attempted to send an email to about 55 recipients using the CiviMail component (see below). I manually initiated it via the Send Scheduled Mailings in the Scheduled Jobs area.

It hangs then displays the DB error message above.

For some recipients, they receive the email multiple times. Others never see it. The report says there are zero successful deliveries, but it also shows tracked opens:

If I try to send another email, it reinitiates the send on emails that have not been cancelled.

I thought I completed a last resort option of rebuilding everything. Since that didn't work, I don't know what to do. I'm desperate for any suggestions.

Answer 1

In all of your database changes, you may have mixed up the database information in one or the other of your civicrm.settings.php files. In Joomla there are two:

administrator/components/com_civicrm/civicrm.settings.php

and

components/com_civicrm/civicrm.settings.php

They should be almost identical: the site URL for the one in administrator should be http://yoursite.org/administrator/ rather than just the base URL of your site.

Both have database connection information; so does your Joomla configuration.php file. You need all three to agree on the Joomla database information (the line with CIVICRM_UF_DSN in the CiviCRM files), and you need the two CiviCRM files to agree on the CiviCRM database information (the line with CIVICRM_DSN).

If you think you've hopelessly ruined your CiviCRM settings files, you can rebuild them from the copy at

administrator/components/com_civicrm/civicrm/templates/CRM/common/civicrm.settings.php.template

You will want to keep your existing ones handy as a guide (and a fallback in case you cause trouble), and you'll need to replace all the tokens, which appear as %%tokenname%% in the file.