Backend is slow after upgrade to 3.0

Try decativating all plugins. If that resolves the issue, reactivate each one individually until you find the cause.

I deaktivated all plugins before I upgrade. And it was slow from the first moment.
It′s terrible even openening the plugins area can last for 3 Minutes.

Any other idea?

You may need to optimize the database.

Access your WordPress database via phpMyAdmin (most hosting providers offer this in their control panel), check all of the tables, and choose “Optimize tables” from the pull-down menu.

GOOD Advise!
But it was not the solution. I optimized the tables after your hint. And it seems to be fine. I ran a ping test with no result. The Backend is still unbelievable slow.

And I definatly have no clue whats going on here. Hopefully you have another suggestion. So we can help others who may ran into the same problem.

Let’s see what happens when you increase PHP’s memory allocation.

First, try installing the Memory Bump plugin.

If that doesn’t work, here are four more ways to increase PHP’s memory allocation:

1. If you have access to your PHP.ini file, change the line in PHP.ini
If your line shows 32M try 64M:
memory_limit = 64M ; Maximum amount of memory a script may consume (64MB)

2. If you don't have access to PHP.ini try adding this to an .htaccess file:
php_value memory_limit 64M

3. Try adding this line to your wp-config.php file:
Increasing memory allocated to PHP
define('WP_MEMORY_LIMIT', '64M');

4. Talk to your host.

@cyprus – how many blogs do you have on your system, and did you hit the upgrade button under Site Admin -> Upgrade after you did the initial upgrade?

Hi I ran an info.php and my PHP Memory Limit is 256M
I install Memory Bump with no result.
I added define(‘WP_MEMORY_LIMIT’, ‘128M’); to wp-config.php

I′ve got 5 Blogs running right now but I want to run approxmatly 200 in the future.
I made the Upgrade but I got this message: Couldn’t resolve host blog.main.com

The backend is still slow like a turtle

Okay I′ve got it.

Every hint you gave me was important and good to keep in mind.
But the solution was different.
I missed a single step in the upgrade routine. After I loaded up the new files to my server I DID NOT run the upgrade prozess cause it was not written in the tutorial I used

So my solution after uploading your files run /wp-admin/upgrade.php
which may look like this on your server
https://www.testblog.org/wordpress/wp-admin/upgrade.php

Thats it . Happy blogging.