The ^DATABASE routine in %SYS allows you to edit the size. Sizing a CACHE.DAT avoids the on the fly expansion that would otherwise happen. Some people thought this would be a performance benefit.

Intersystems has worked hard but encryption is not free. Do you have something like batch processing? You would notice an impact more there then on a 1 second query. I would worry more about key security and recovery. Encryption also has a serious impact on the ability of modern SAN storage to dedup and compress which could result in higher than expected storage costs.

If you have not already, migrate to solid state disks.

It is weird that the page Vic recommends does not mention that.