We would like to intall 2 CA products, CA Service Desk and CA Identity Suite 14.2 Virtual Appliance These two would share the same SQL Server 2016 Database engine, would you please provide the memory requirement for such configuration?
I cannot recall there is a minimum memory requirement.
I think it depends on a lot of factors...how big the databases are going to be, what kind of dbms performance is acceptable etc. The OS itself can use virtual swap memory if necessary and of course you will have a lot of IOs and performance to play around.
Yes size is the factor, 12GB minimum by default for most installs of SDM:
Server and Hardware Requirements - CA Service Management - 17.1 - CA Technologies Documentation
Perhaps 16GB as that is recommended by Identity Suite:
Installing Virtual Appliance - CA Identity Suite - 14.2 - CA Technologies Documentation
Chi is also right though - it depends a lot on what goes through the databases.
I think most site DBAs tend to get memory allocation to database allocations right, as it is one of those easier to spot red flags if it is not working. It is more likely down the track with index monitoring on queries that are likely to throw up performance issues if they are not done.