Obtain an SVC dump by:
- Using a SDUMP or SDUMPX macro in an authorized program.
- Entering the DUMP or SLIP operator command
- Setting a SLIP in the IEASLPxx parmlib member.
When z/OS® takes an SVC dump,
it copies data into the DUMPSRV owned data spaces and high virtual
storage. The collection of data can introduce an unusually heavy burden
on storage resources. The virtual storage load remains until the dump
is written out to a target data set on DASD. The data set can be:
- SVC dump data set that is specified on the DCB parameter of the
SDUMP or SDUMPX macro.
- Pre-allocated SYS1.DUMPxx data set, or automatically allocated
dump data set.
Use the DUMPDS operator command to manage the pre-allocated and
automatically allocated data sets.
When an SVC dump occurs, if normal auxiliary storage use rises
above 30%, the system might experience severe performance problems.
The system might also experience an 03C wait state, which indicates
that the system ran out of available paging slots. You can use the
MAXSPACE and AUXMGMT options on the CHNGDUMP SET, SDUMP command to
manage the burden of taking SVC dumps on a system. Using the options
might not be sufficient to eliminate the problems that are associated
with the restricted auxiliary (paging) storage.
- The MAXSPACE value restricts the virtual storage available to
the DUMPSRV address space. When you use MAXSPACE, the installation
must tune for the worst case usage of real and auxiliary storage.
The following rules apply:
- If the installation does not have a history that can be drawn
upon, see Allocating SYS1.DUMPxx data sets with secondary extents for help in determining
a maximum data set size. Use a multiple of the data set size to determine
a MAXSPACE value. The installation must predict the size of the largest
dump that it can configure.
- The paging resources for the affected systems must also be increased
to accommodate the additional load that is represented by the MAXSPACE
value. The minimum value for defining the additional auxiliary storage
capacity must be three times the MAXSPACE value. Adhering to the MAXSPACE
guideline can maintain utilization within 30%.
- When you specify the AUXMGMT=ON parameter, the installation disregards
first failure data capture (FFDC) to maintain system availability.
The following rules apply:
- No new dumps are allowed when auxiliary storage usage reaches
50%. New dumps can be initiated after the auxiliary storage usage
drops below 35%.
- Current SDUMP data capture stops when auxiliary storage usage
exceeds 68%, and generates a partial dump.
For more information about setting the MAXSPACE or AUXMGMT value,
see the
CHNGDUMP Command in
z/OS MVS System Commands.
Requesting dumps from multiple systems
In a sysplex, you probably need dumps from more than one system
to collect all of the problem data. These dumps must be requested
at the same time. To request multiple dumps, use the following procedures
on any of the systems that might be part of the problem:
- Enter a DUMP command with a REMOTE parameter.
- Issue a SDUMPX macro with a REMOTE parameter.
- Create a SLIP trap in an IEASLPxx parmlib member in the shared
SYS1.PARMLIB or in the parmlib on each system.
- Sometimes you cannot predict which system has the problem. Use
a ROUTE operator command to activate the traps on all systems with
similar configurations. Each trap must include a REMOTE parameter
to dump all the other systems that might be involved.
To help you set the requests, the commands and macro can contain
the wildcard characters * and ?.
Use wildcard characters when an installation has names that form patterns
to the systems in the sysplex and to the jobs for associated work.
For example, use wildcard characters * and ? to
specify job names. Use TRANS? for the job names TRANS1,
TRANS2, and TRANS3 and TRANS* for TRANS1, TRANS12,
and TRANS123.