Can the SYS1.CACS.CAILOAD dataset, in the CDMSLIB DDname concatenation, be deleted from the system startup JCL?
The loadlib noted here, SYS1.CACS.CAILOAD, is one of the CA Common Services libraries. This was required in the CA IDMS CDMSLIB concatenation up through IDMS R15.0. However, as of r16, the ADS tools no longer require the CA90s Common Service libraries. So you should be safe to remove the SYS1.CACS.CAILOAD library from your CDMSLIB of your 18.5 procs.
If your procs invoke the CA IDMS Server, and if that server is establishing a CCI connection to CA IDMS instead of a TCP/IP connection, they you might still need the library in your proc, because the CCI modules are in those Common Services libraries. In all other situations you should be OK to remove them, though as always we suggest that you test the changes before moving them into production.