First you can see if your site has JCL that assembles and Links the IN25UCOM core commands. But just because you cannot locate JCL does not mean you are not using custom IN25UCOM core commands. If you browse the release 8.5 HLQ.CACICSXX load library(XX is the CICS level) a default IN25UCOM member is shipped with the product. You will need to open a case with CA support and find out what the default size is for the release r 8.5 IN25UCOM load library member. If your IN25UCOM is larger than the default shipped with the base install, then you are using custom IN25UCOM core commands.