You go to transaction SM51, select one of the application servers with a "single-click" and hit the "Release Info" button.

Then you scroll down to the end and see the lib_dbsl patch level in the last line. Usually, you will detect, that many patches are increasing and then "suddenly" - nearly at the end - they begin with a lower level again. These are then the lib_dbsl patches. Unfortunately they are not really good described. You have to know this "feature".
You should compare this with the current patch level at SAP. If the difference is large, you should think on updating this patch, even when you do not have problems at the moment. But, the Kernel Patch level is a lot more critical than the lib_dbsl Patch level. So, this is normally not a real problem.