During the initial discussions it was determined that the "outages" were in fact PHP script errors, which in some server configurations are disabled by default, displaying a rather useless blank white screen instead.

You can easily enable error reporting by using a local PHP override either in a php.ini file or, if that won't work, setting PHP flags inside your .htaccess file:

php_flag display_errors on

As soon as the errors were being displayed, the problem was indeed revealed as a PHP script error:

Warning: include_once() [function.include-once]: Unable to allocate memory for pool. in /var/www/vhosts/httpdocs/app/Mage.php on line 49

Whilst not immediately useful, it does at least provide some food for Google in order to begin a search for potential solutions. During this research phase, I actually turned up very little relating to Magento specifically, but there was quite a lot of information in relation to PHP. In many cases, an Apache module known as "APC" kept cropping up. Apache APC ("Alternative PHP Cache") is "a free and open opcode cache for PHP. Its goal is to provide a free, open, and robust framework for caching and optimizing PHP intermediate code.".

A quick check of server options using phpinfo(); confirmed that APC was indeed running on the server.

The Solution: Disable APC

I find the Magento's cache system quite comprehensive, and set-up correctly should provide an adequate caching system/performance boost for your Magento site. If you have alternative thoughts or can offer more information on how APC can benefit a site, I'd welcome your comments.

So, in this case, I decided to disable the APC module for this particular virtual host on the server (this way it's still available for other sites running on the server). Disabling the module is very simple, and easy enough to re-enable if you need to do so in the future. It requires another line added to your .htaccess file:

php_flag apc.cache_by_default Off

You can re-run phpinfo(); again to confirm the APC is disabled correctly – and of course, test the live site to see if it fixes your problem!

The problem is that in-development stores need testing; to do that properly, you need to push test orders fully through the system, from invoice to completion.

The first thing you need to bear in mind is that, whilst this is possible using a load of MySQL queries, that kind of thing on a working site is pretty scary and risky if you're not sure what you're doing. For this reason, I would recommend purchasing the Yireo extension Delete Any Order which will do the job for you. It will also scan the database for orphaned sales data and remove, something which would take significant time by hand.

The extension costs a mere EUR20 and is worth it just for the piece of mind. Whatever you choose, please ensure you backup your database first.

Deleting the Orders

Once you've purchased the extension, upload it to the root of your Magento site.

This will give you an additional option in System->Tools called "Delete Any Order". Select it to run the extension.

If you are preparing a store for launch and want to remove all orders and reset the sales reference numbers, select all orders and choose the "Delete" option from the drop-down menu (top-right).

Reset the Counters

You don't really want your new store starting orders, invoices, shipment and credit memos from some random number do you? Do the following to reset these counters to the default (1000001).

1. Use PHPMyAdmin to view your database.

2. Click the "SQL" tab.

3. Paste the following query into the code entry window:

TRUNCATE `eav_entity_store`;
ALTER TABLE `eav_entity_store` AUTO_INCREMENT=1;
SET FOREIGN_KEY_CHECKS=1;

4. If all goes well, the system will display a message stating that the query was a success.

The next order placed will now use the default number to start.

I recommend testing these steps out on a test site rather than your live environment, if that's possible – just so that you are comfortable with the steps before deploying on a live site.

The following article describes the processes and steps involved to successfully move your Magento site to a new server/domain name, along with some possible solutions for further issues you may encounter.

1. Package up and/or download the site files

I used my Control Panel’s “site backup” feature here for two reasons: a) you have less to download, and b) you can be sure you have all the files intact when you deploy the other end.  If you don’t have this feature with your host, you can manually download the files – but be sure to check you have everything and that there were no errors during the downloading process!

Also, if you have shell access to the server, you can zip up the whole lot and download in one go – this will make it easier to deploy on the receiving end, and will ensure none of the files are corrupted and/or go astray during the upload.

Once I had my package downloaded, I deployed to the new server – again, if you can, upload the zip package and extract via the server.  If you are unable to do this, extract the package locally and upload the files manually (cue: cup of tea).

2. Take a backup of the original site’s database

Using PHPMyAdmin, take a full backup of the site database that Magento was using.  This should be in the form of a .sql file.  Make sure you take a full backup of all the database tables. If the database is particularly large, use compression on the export (built-in to PHPMyAdmin) which will help keep within the file upload limits.

3. Import the SQL file into the new database

Working in PHPMyAdmin on the target server, simply import the SQL file into an empty database (you may need to create one first).

4. Update the live site URL data in the database

This needs to be done in two places in the database.  Using PHPMyAdmin, select the table named core_config_data and locate the following database rows:

web/unsecure/base_url

web/secure/base_url

Note the text value for each entry – this corresponds to the root URL of the site.  This should be confirmed as the data should reflect the current site’s root URL.  To change, simply click the edit button for each of the two rows and input your new base URL value into the text box, saving when you’ve finished each one.

5. Update local.xml with the new configuration details

You can find your local.xml file in the app/etc directory.

Look through the file until you see the database connection information.  If will look similar to the following:

<default_setup>
  <connection>
     <host><![CDATA[localhost]]></host>
     <username><![CDATA[my_user]]></username>
     <password><![CDATA[my_pass]]></password>
     <dbname><![CDATA[my_database]]></dbname>
     <active>1</active>
  </connection>
</default_setup>

Then change the values in the square brackets after the CDATA tags to your new database server settings, for example:

<username><![CDATA[mynewusername]]></username>

Once done, save the file.

6. Delete the cache data

Simply locate your var folder and delete all content within.

You may also need to manually deploy the .htaccess file from the old site to the new site – so if your links do not work on the new server, make sure .htaccess is present and correct.

Problem 1: MagentoConnect No Longer Works

If you are planning to update Magento Core, any modules, or add new extensions to your Magento site, you will need to correct this since the Connect Manager (/downloader on the server) references the old site, and the links are hard-coded into the files, making it practically impossible to update manually. There is also a real risk of accidentally updating files on the old server if running MagentoConnect (if the old site still exists).

The best way to sort this problem is this:

1. Delete or Rename the /downloader directory

Probably safer to rename this for the time being. You will need to do this via FTP or your control panel file manager.

2. Obtain a fresh copy of Magento

The version number will need to be the same as the version you are running on your site. Download the .zip file and extract locally to your computer.

3. Upload the "clean" /downloader directory

Once you have the extracted files from step 2, find the /downloader directory and upload it to your Magento installation.

4. Run MagentoConnect and perform a core update

You can leave this step for now if you prefer not to update your installation. This will check all core modules and update as necessary, and will also add the missing list of core modules back into MagentoConnect. Paste the following extension key into MagentoConnect Manager:

magento-core/Mage_All_Latest

You can also do this for any extensions you have installed, which will also add them back into the list.

Problem 2: "Notice: Undefined index" Error when running the site

This could be caused by an error during the MySQL import and is possibly related to auto-increments on certain rows in the database.

Try this and see if it fixes the problem:

1. Logon to PHPMyAdmin.

2. Locate the following tables: "core_store", "core_store_group" & "core_website".

3. Note the "website_id" value for the admin code. It should have a 0 (zero) value; if not, change it to zero and save. Repeat this for all three tables.