A dump records or copies, at a particular instant, data
from one storage device onto another storage device to protect the
data. Dump data is extremely useful when debugging the problem.
- SVC dump
- An SVC dump provides a representation of the virtual storage for
the system when an error occurs. Typically, a system component requests
the dump from a recovery routine when an unexpected error occurs.
However, an authorized program or the operator can also request an
SVC dump when diagnostic dump data is needed to solve a problem. Complete
details are found in SVC dump in z/OS MVS Diagnosis: Tools and Service Aids.
- Transaction dump
- A transaction dump provides a representation of the virtual storage
for an address space when an error occurs. Typically, an application
requests the dump from a recovery routine when an unexpected error
occurs. Complete details are found in Transaction dump in z/OS MVS Diagnosis: Tools and Service Aids
- Abend dump
- An ABEND dump shows the virtual storage predominately for an unauthorized
program. To produce a dump when one is requested for an error, a JCL
DD statement of SYSUDUMP, SYSABEND or SYSMDUMP must be included in
the input job stream. See z/OS MVS JCL Reference for
more information. An operator can also request an ABEND dump while
ending a program, an address space, or canceling a job. There are
three types of abend dumps:
- SYSMDUMP – Is an unformatted dump that requires IPCS to view and
format. Unformatted dumping is sometimes more efficient because only
the storage requested is written to the data set, which means the
application can capture diagnostic data and be brought back online
faster.
- SYSABEND – The largest of the ABEND dumps, is a pre-formatted
dump containing a summary dump for the failing program plus many other
areas useful for analyzing processing in the failing program.
- SYSUDUMP – The smallest of the ABEND dumps, containing data and
areas only about the failing program.
Complete details are found in Abend dump in z/OS MVS Diagnosis: Tools and Service Aids.
- SNAP dump
- A SNAP dump shows virtual storage areas that a program, while
running, requests the system to dump. A SNAP dump, therefore, is written
while a program runs, rather than during abnormal end. The program
can ask for a dump of as little as a one byte field to as much as
all of the storage assigned to the current job step. The program can
also ask for some system data in the dump. A SNAP dump is especially
useful when testing a program. Complete details are found in SNAP dump in z/OS MVS Diagnosis: Tools and Service Aids
- Stand-Alone dump
- The other tools discussed in this chapter are used to collect
data for individual work units on a system or a subset of components
on a system. A stand-alone dump is used to collect diagnostic information
about the entire system. Stand-alone dumps are not produced
by z/OS but by an either the IPCS SADMP dump data set utility or the
AMDSADDD REXX utility. After a stand-alone dump is taken, because
the system cannot resume normal processing, the IPL is of the stand-alone
dump instead of z/OS.
The stand-alone dump program produces a stand-alone
dump of storage that is occupied by either:
- A system that is stopped. For example, your installation has a
wait state with no processing, so you must capture a stand-alone dump
to diagnosis it.
- A stand-alone dump program that failed. Either the stand-alone
dump program dumped itself — a self-dump —, or the operator
loaded another stand-alone dump program to dump the failed stand-alone
dump program.
The stand-alone dump program and the stand-alone dump
together form what is known as the stand-alone dump service aid. The
term stand-alone means that the dump is performed separately from
normal system operations and does not require the system to be in
a condition for normal operation. It is essential to perform a store
status before taking a stand-alone dump because the program gets loaded
over storage that might be needed in the dump.
For more information,
see the complete details in Stand-Alone dump in z/OS MVS Diagnosis: Tools and Service Aids and
in Stand-alone dump best practices in z/OS
Problem Management.