If you plan to change the database from Oracle to Microsoft SQL Server for Service Desk usage, there is no documented procedure how to migrate between these two types of database because databases are third-party products. However, from the Service Desk perspective it can be similar when test/QA servers with production data is built. In that case, only data is moved from production to other environments, including few parameters that can be moved manually. In the case of changing the database vendor, it has a similar approach, because data can be moved through the Service Desk tier, without being specific regarding the database.
It means you are able to move data using Service Desk tools such as pdm_extract/pdm_backup and pdm_load/pdm_restore.
On the other hand, if you wish you can use database tools to move around the data from one database to another. Check in Microsoft SQL Server or Oracle side if there is any procedure for moving data between them. You have to talk with your database vendor in order to find ways to migrate databases between different vendors.