For branch entry to SDUMP, there are two types of summary dumps:
- Disabled summary dump - which performs the summary dump with the
system disabled for interruptions. This means that all data to be
dumped must be paged in at the time of the summary dump.
- Suspend summary dump - which is taken in two parts. The first
part is similar to the disabled summary dump and dumps some of the
global system control blocks. The second part runs with the system
enabled for interruptions. This allows data to be dumped that is currently
paged out, but was going to be modified by the recovery routine that
requested SVC dump processing.
The SUMDUMP output for a branch entry to SVC dump might not match
the data that is at the same address in the remainder of the dump.
The reason for this is that SUMDUMP is taken at the entry to SVC
dump while the processor is disabled for interruptions. The system
data in the remainder of the dump is often changed because other system
activity occurs before the dump is complete. The SUMDUMP output follows
a header that contains the ASID of the address space from which the
data was obtained.
The following conditions can occur that prevent SDUMPX from taking
a disabled or suspend summary dump.
- The system is not able to obtain the necessary locks to serialize
the real storage buffer (RSB).
- The system is in the process of modifying the storage queues and
cannot satisfy the request for a RSB.
- No frames are available for a RSB.
- SVC dump encounters an error while holding serialization for the
RSB.
- A critical frame shortage causes the system to steal the pages
of the RSB.
- The SVC dump timer disabled interruption exit determines that
SVC dump has failed and frees the RSB.