In order to check errors it is good to switch debugging on while you are testing your upgraded Typo3 installation.

Go to the part „configuration“ in your Typo3 backend:

Under the tree item „SYS“ you can configure the debugging:

Set the following parameters in you localconf.php:

$TYPO3_CONF_VARS['FE']['debug'] = '1';

$TYPO3_CONF_VARS['SYS']['sqlDebug'] = '1';

$TYPO3_CONF_VARS['SYS']['Debug'] = '1';

$TYPO3_CONF_VARS['SYS']['displayErrors'] = '1';

$TYPO3_CONF_VARS['SYS']['devIPmask'] = '*';

Since version 4.2.0 the charset is set to UTF-8. This means you might need to change special characters. The best is to use HTML signs for special chars! A good resource for this is http://www.asciitable.com/

If you have own classes and database connections (even in external files and included over content type PHP), you need to change them as well! Check that the right database is being selected and all paths are correct! I had global Typo3 errors, because of errors raised in external PHP files.

If you use the wysiwyg editor RTEHtmlArea then there is a surprise: This extension is now a system extension and already being delivered with the Typo3 installation. Be sure to deinstall and maybe delete your local version. Then clear all cache and install the delivered system extension. If the editor is not being displayed, the error might be that your local installation is not properly undone.

$TYPO3_CONF_VARS['BE']['RTEenabled'] = 1;

Once correctly installed you may wish to use all options the RTEHtmlArea. Therefore select the following options preset:

Be sure that you have replaced all paths from the old installation directory to the new one. A good way to do this for content in your new Typo3 installation is using „DB check“. For this log on to your Typo3 backend an choose „DB check“. Then select „Search whole database“:

Select „Raw Search in all fields“ as search method and search for the old path:

You can update this directly by using the symbol:

I had installed the date2cal extenion, which makes date fields in the backend selectable by a calendar:

I needed to update this extension to a new version. Then it worked again.

I needed to change my secondary website language, because new flags were delivered:

My tt_News did not work anymore. Error message was something like „invalid locallang.xml“. I have downloaded the single file „locallang.xml“ from the Typo3.org repository. Then it worked for me. Be sure to download locallang.xml for the right version of your tt_news installation.

The indexed search did not work anymore. Here you may use a new configuration for it. I have decided to use the old version as it was easy to implement again.

Clear all cache and index tables in your database (index_*, cache_*). Then you have to reindex the entire site. A good way to reindex an entire website is an offline browser like HTTRACK http://www.httrack.com/. With the call of each site, the called sites will be indexed.

In the backend while editing a template in the object browser: The left scrollbar was missing. So I had to change the file typo3/alt_mod_frameset.php by changing „frame list_frame option scrolling="yes"“.

I had installed the extension dh_linklayout, which enables you to configure an own rendering for your links. After the upgrade it did not work anymore. I needed to reinstall it and configure it new.

It is, especially when you let host your site by en external hosting provider, advisable to check the Typo3 performance. I had several problems after the upgrade. Things you can do are:

Set Memory Limit

Index on MySQL tables

Check especially that large and often used database tables are inddexed correctly.

Load Control

It may be necessary, especially if you have a low performance server of a public hosting company, that you limit number of users and reloads of your website. Therefore I am currently developping a new extension. See point „Typo3 Load Control“ later in this document.

If you use Typo3 cache system and you use a custom rendering part in your template of type „USER“ you may change it to „USER_INT“. This way the content will be dynamic (important for counters etc.).

You may need to do the following things:

$TYPO3_CONF_VARS['FE']['maxSessionDataSize'] = x;

$TYPO3_CONF_VARS['FE']['lifetime'] = x;

$TYPO3_CONF_VARS['FE']['maxSessionDataSize'] = x;

(x = number)

It may be necessary, especially if you have a low performance server of a public hosting company, that you limit number of users and reloads of your website. Therefore I am currently developping a new extension called „mv_typo3_load_control“.

That was it :-)