When upgrading your XenDesktop 5.5 environment to XenDesktop 5.6 make sure you have read the following to be successful in your upgrade.
This post describes how to upgrade a small XenDesktop 5.5 environment to XenDesktop version 5.6.
Best Practice for Upgrading a XenDesktop 5 Site
Refer to the specific documentation related to the released version of XenDesktop that you are using for any release-specific detail. Specific documentation can be found on Citrix eDocs. When upgrading an existing XenDesktop 5 site to a new release or applying a hotfix, the following best practice procedure is strongly recommended: