Obtaining information about CSECTs in the DAT-ON nucleus (NUCLKUP)

IPL processing places the CSECTs located in the DAT-ON nucleus in virtual storage and creates a map of them. The real addresses do not equal the virtual addresses and the real addresses are not necessarily contiguous. IPL processing loads the CSECTs into storage according to residency mode and according to whether they are read only or read/write. If the CSECT is assembled with RMODE=ANY, it is placed in the extended nucleus. Figure 1 shows the virtual storage map of the DAT-ON nucleus.

The nucleus map look up service provides users with information about these CSECTs. Through the use of the NUCLKUP macro, users can perform two functions:

• Retrieve the address and addressing mode of a nucleus CSECT, given the name of the CSECT
• Retrieve the name and entry point address of a nucleus CSECT, given an address within the CSECT.