If we are using Microsoft Dynamics CRM 2015 compatible servers, we can go with the in place upgrade option, but this option is not recommended for upgrade because it involves a great risk of downtime in case of any issues occurring during upgrade. It can also corrupt the complete database, so it is always recommended that you create a VM from the existing CRM deployment and do a trial upgrade there instead of directly upgrading the real CRM servers. Also, we should always keep a complete copy of the CRM database before planning an upgrade.

This option requires a different server setup, but still this is the recommended method of doing an upgrade because it involves less downtime. We can use two methods of migration upgrade. One option is to use different servers for the CRM application and CRM database. The other option is to use different servers for CRM application and use the existing CRM database server that is compatible with Microsoft Dynamics CRM 2015 SQL server requirements.

We can select the upgrade option based on the infrastructure, but the only possible upgrade path to Microsoft Dynamics CRM 2015 is from Microsoft Dynamics CRM 2013 Service Pack 1 (SP1). This means if we are using Microsoft Dynamics CRM version earlier then 2013, we need to first upgrade to Microsoft Dynamics CRM 2013:

So, let's say if you are using Microsoft Dynamics CRM 4.0 and want to upgrade to Microsoft Dynamics CRM 2015, you need to follow sequential setups explained in the preceding screenshot to upgrade. It is recommended to clean the organization's data before upgrading to CRM 2015. Some of the upcoming functionality depreciated from CRM 2013 version, so if we are upgrading to CRM 2015 from CRM 2011, we need to clean the organization's data based on these points.

Support for Microsoft Dynamics CRM 4.0 web service endpoints (known as 2007 endpoints) is not supported by CRM 2015, so if you are using 2007 endpoints in your code, you need to update your code to use OData endpoints or SOAP using 2011 WCF endpoints before upgrade.

Microsoft Dynamics CRM 2015 does not support the CRM 4.0 object model. So, if there is any client-side code written using the CRM 4.0 object model that needs to be changed to a similar CRM 2015 object model, we can use the CRM 2013 custom code validate tool to detect scripting, which is written using CRM 4.0 standards.