Hi @Lee John Li ,
RTM stands for Release to Manufacturing, which is the original release version of the product.
Cumulative Update (CU): Cumulative update package, which consists of Hotfixes. CU is released every 8 weeks, so there will be CU1, CU2 ......, etc. Each latest CU version contains Hotfixes from the previous CU. CU is installed based on the original version (RTM) or SP.
Service Package (SP): SP is the package with the most integrated Hotfixes, which are officially and fully tested. SP is the largest patch file for a SQL Server product release, and is released every 12 to 18 months.
GDR (General Distribution Release) is different from CU in that each latest CU contains cumulative updates based on RTM/SP, while GDR contains only serious updates. They have the same baseline.
Each latest CU contains fixes for issues integrated with the previous CU, and each SP contains fixes for issues included in the previous SP. Now look at the picture again.
So, in order for you not to miss any fixes, I suggest you install the latest SP3 first and patch it with GDR. See this document: KB3177312 - SQL Server 2016 build versions.
Best regards,
Seeya
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