Magento Extension is a simple way of adding new features to the existing magento store. There are basically two ways of installing a magento extension.
1. Using magento connect.
2. Using FTP to install the magento extension.
If you are using a commercial extension which you have purchased from the merchant’s site then you will receive the extension in zip files.
In this case you have to install the extension by following the second method, which means that you have to copy the extension files on to the server using FTP.
But wait!! This is not enough.
You have to follow proper steps for that.
1. Always take the backup of the database before installation of extension so in case of any issue you can restore the whole system.
2. Put the store to maintenance mode.
**Many will doubt the need of doing so, but this is really important. The secret lies in the way magento executes its installation process.
Now suppose you are transferring the files of your extension files using ftp and in the middle of the transfer someone makes a http request on your magento store. As soon as magento gets a request it will first check whether there is some new installation or not. If it finds the module xml file then it will execute and complete the installation even if the file transfer is not complete which can result in errors in your store. Putting magento in maintenance mode prevents this problem from happening.
3. Follow the extension instructions and copy the files to the respective folders.
4. After the file transfer is complete, remove the maintenance flag and run the magento store which will initiate and complete the installation.
5. Clear the cache.
You have successfully installed the extension. HURRAY!