CICS® system dumps and transaction dumps are written unformatted to the appropriate dump data set. In other words, they are memory dumps of all or part of the CICS address space.
Unformatted dumps are not easy to interpret, and you are recommended not to use them for debugging. CICS provides utilities for formatting transaction dumps and CICS system dumps, and you should always use them before you attempt to read any dump. You can quickly locate areas of storage that interest you in a formatted dump, either by browsing it online, or by printing it and looking at the hard copy.
The formatting options that are available for transaction dumps and system dumps are described in Formatting transaction dumps and Formatting system dumps, respectively.