The question is a bit vague for me, so I’ll answer the database question as 2 interpretations -
Compatibility - 9.12 IS, MWS, Monitor, Process Engine and Trading Networks are compatible with 19c and JDBC Adapter 9.10 is compatible with 19c. However, other products such as Business Console are incompatible, so give the documentation a check against what you have in your environment. Ensure that you have the right drivers in place.
wM product system requirements are here on page 5, while JDBC Adapter is here on page 28.
Impact - Naturally, I assume that your DBAs are upgrading the database on a side-by-side or cross-host approach. Since IS is compatible with both 12c and 19c, I may reasonably assume that there won’t be major issues. However, I suggest that you understand what is changing from 12c to 19c, from an Oracle perspective, so you know are not flying blind.
I recommend that you exercise usual caution - upgrade your lower environments first and go through a strong test cycle, since you are swapping DBs and data (i.e., essentially a transplant along with blood transfusion). Perform a full mock cutover on a functional environment that’s closest to PRD (such as PREPRD/QA). Ensure that you have reliable backups and a rollback plan.
Oracle EBS - I’m unfamiliar with Oracle Apps Adapter, but the compatibility matrix doesn’t include 12.2.10 (page 41) here.
Note - Pose a formal question to Software AG product support, so you can get an official confirmation and/or better recommendations.