TYPO3 Core

should be "When trying to upgrade 4.3 to 4.4.10"...

Yes, 4.3 did work correctly.
I didn't change anything. I know database settings in localconf.php, they are correct,
but something just stuck. MYSQL version is the same. Maybe minimize localconf.php just to basic extensions and configurations and test?

Reducing localconf.php to only the 3 lines with the database credentials $typo_db_username, $typo_db_password, $typo_db_host will break almost everything in your installation, but only for checking the DB access in the Install Tool it should be enough.

Do you use dbal? This might influence behaviour here.

I tried it without dbal, tried with empty localconf, having only database settings. The same.
I have noticed similar problems in http://forge.typo3.org/issues/21632
but it seems no consensus was reached about this problem.

This might be a problem with persistent connections in MySQL.

Edit the file t3lib/class.t3lib_db.php: In the function sql_pconnect(), directly below the line $error_msg = $php_errormsg; add this:
echo $this->link;
echo $error_msg;
die();

I guess that $this->link is empty. $error_msg will contain the according error message.

Try setting $TYPO3_CONF_VARS['SYS']['no_pconnect'] = 1 in the Install Tool.

Thank you. Got this error:
mysql_pconnect() has been disabled for security reasons

So it's a hoster's problem..?

Maybe it would be worth to add some error report about not working mysql_pconnect() to Install tool?
I remember I had exactly the same problem with former hosters.

With

$TYPO3_CONF_VARS['SYS']['no_pconnect'] = 1

it worked. Thanks!

A hint to check $TYPO3_CONF_VARS['SYS']['no_pconnect'] would have helped you.

The text of the error message is incomplete and in so far wrong.

To fix it we could add to the error message, that this error could also be caused by "persistent connections" in MySQL being forbidden and that this is fixable with setting $TYPO3_CONF_VARS['SYS']['no_pconnect'] = 1.

What do you think?

We could add to the error message, that this error could be caused by "persistent connections" in MySQL being forbidden >and that this is fixable with setting $TYPO3_CONF_VARS['SYS']['no_pconnect'] = 1.

I think it would be great, since I noticed I was not the only one, and while looking for solution, found quite many similar questions in forums. Without error report one just searching for many various possible things. Simple error report would minimize possible confusion and would narrow possible search + save time.

I'm not sure if it would fit into current Install tool concept, but I think simple base system (server+database) configuration check and reporting (it could be visual or just a simple log) could help in determining possible roadblocks for the average user.

Thank you very much for the help.

Patch set 1 of change I28f373c1e771f00d1584eff5080bfa51cf48ed96 has been pushed to the review server.
It is available at http://review.typo3.org/4633

Patch set 2 of change I28f373c1e771f00d1584eff5080bfa51cf48ed96 has been pushed to the review server.
It is available at http://review.typo3.org/4633

Patch set 3 of change I28f373c1e771f00d1584eff5080bfa51cf48ed96 has been pushed to the review server.
It is available at http://review.typo3.org/4633