How would be the best approach from you side for below change.
Custom Field Customer needs to be a multi-select dropdown rather than free form text. This will allow us to create portlets with "Customer" as one of the fields.
There are a number of aspects to this task:
data cleanup of existing records. For example, some tickets have custom field values as VZ, Vz or Verizon. All of these must be cleaned up.
how the migration will deal with tickets that have multiple customers in the free text field