Prior to migrating a site it is absolutely essential that your database and all files be backed up . It is recommended that you migrate on a copy of your database while leaving your existing site in operation. Once you are satisfied that your 1.5 site is working as expected, you can switch to the new site. If this is not possible because your host limits the number of databases you have available, you can still install the 1.5 files in a new folder. In this situation, you should use the global settings on your old site to take the site offline while you make the transition.
To make a backup of your site, you must backup both the files and the database. There are several extensions which can help with this or you can use the options offered by your host. Ask your host for instructions on how to do a backup if you are unsure.
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