Nucleus Load Map

A nucleus load map (NUCMAP or load map) is a file that contains the following information:
  • A list of the storage addresses of all control sections (CSECTs). A control section is the part of a program that the programmer defines as a relocatable unit. It is a block of code that can function properly in any part of storage. All elements of a CSECT are loaded into adjoining locations in storage.
  • The storage addresses of all modules loaded into the CP nucleus, CMS nucleus, or GCS nucleus. The CP nucleus contains that portion of CP resident in host storage. Similarly, the CMS or GCS nucleus is that portion of CMS or GCS present in virtual storage.
  • A list of all modifications performed on the modules in the nuclei. This includes all the maintenance that IBM® has performed on the modules and all the modifications your organization has made to them.

One load map exists for CP, another for CMS, and another for GCS. z/VM® creates a load map each time CP or CMS is built—that is, when your system is first installed or after it is repaired or modified. 1 In this manner the load maps are kept up to date.

Load maps are useful particularly when you are dealing with an infinite loop. Load maps also complement the information found in a dump. When you use one, you should have the other handy.

Load maps can be found in the following locations:
  • The CPNUC MAP file, on the MAINT virtual machine's disk at virtual address 194, contains the CP NUCMAP.
  • The CMSNUC MAP file, on MAINT's disk at virtual address 193, contains the CMS NUCMAP.
1 These activities are performed by the system programmer or system operator using the MAINT virtual machine. This is the virtual machine you use to install, service, and maintain your z/VM system. The z/VM: Installation Guide and z/VM: Service Guide explain these activities.