CRM upgrade is a process of renewing outdated software that no longer satisfies organization needs. If the company is using SaaS CRM (Software as a Service), it would mean updating to the newest software version.
In the case of custom CRM software, it would mean a whole package of the software development process. It will include current software analyses, planning, few steps of realization, adjustments, and testing. Depending on company needs, CRM software can be converted to new technology (for example, migration to .NET), transferred to another data store type (ex, on-premise server to cloud), and more.