Sitecore provides update installation guide for each version, please find it on this page - https://dev.sitecore.net/Downloads/Sitecore_Experience_Platform/101/Sitecore_Experience_Platform_101_Update2.aspx
This guide clearly says that the release of Sitecore XP 10.1.0, Sitecore update releases do not contain any breaking changes or database changes. The upgrade process from an earlier version in the Sitecore XP 10.1 series to Sitecore XP 10.1.X has therefore become much easier and all the required steps are described in this guide. Before updating your Sitecore XP production system, we recommend that you test the update process on a test or developer system. This can highlight issues that may be caused by any custom tools and applications that you are using.
Adding high-level steps here for your Sitecore 10.1.0 to 10.1.2 -
- Install the new Sitecore 10.1.2 and any modules that you are using besides your existing Sitecore XP installation.
- Connect the new installation (CM,CD,Xconnect,Identity Server) to your 10.1.0 databases
- Connect the new installation to your Solr indexes
- Import the client languages.
- Deploy your solution on top of the new installation -
Depending on your development process, you should
- In your solution, reference the new Sitecore XP 10.1.X components and
assemblies. Nuget or Local references of dlls
- Ensure that any configuration changes you have implemented are reconfigured in separate configuration patch files, if you already not have it in the solution.
- Edit the Web.config file and any other non-patchable configuration files to meet your needs.
- Perform the post-upgrade steps (optional).
Clear the browser cache.
Republish your website to every publishing target.
Rebuild the content search indexes.
Rebuild the link databases.
If you are using xDB, you can:
For more please see the update installation guide from this link.