Let me try to understand.
You run PDI jobs (I don't know what's PDI, but it's probably not relevant right now). Originally, you could not run them because you didn't have enough memory. You added swap space, and now you don't experience memory shortage, but jobs are very slow.
If I understand you correctly, my opinion is that the jobs overload the system. You need more than 16GB of RAM.
You can double-check this with a command like
vmstat, which reports virtual memory statistics. Run it like this:
which means that it will display statistics ten times, and every three seconds. Pay particular attention to the
swap and
io values.
Or
Here, the
pg... metrics are interesting, in particular
pgpgin/s and
pgpgout/s, meaning pages paged in and out, respectively.
You can also use the
free command to see how much RAM is available, but it's easy to interpret its output incorrectly.
sar and
vmstat may not be on your system. In this case, use your software management tool to install them.