Technical data

SDA Description
2.1 Invoking SDA
If your process satisfies these conditions, you can issue the DCL command
ANALYZE/CRASH_DUMP to invoke SDA. If you do not specify the name of a
dump file in the command, SDA prompts you for the name of the file, as follows:
$ ANALYZE/CRASH_DUMP
_Dump File:
The default file specification is as follows:
disk:[default-dir]SYSDUMP.DMP
disk and [default-dir] represent the disk and directory specified in your last SET
DEFAULT command.
2.2 Mapping the Contents of the Dump File
SDA first attempts to map the contents of physical memory as stored in the
specified dump file. To do this, it must first locate the system page table (SPT)
among its contents. The SPT contains one entry for each page of system virtual
address space.
The SPT appears at the largest physical addresses in a typical configuration. As
a result, if a dump file is too small, the SPT cannot be written to it in the event
of system failure.
If SDA cannot find the SPT in the dump file, it displays either of the following
messages:
%SDA-E-SPTNOTFND, system page table not found in dump file
%SDA-E-SHORTDUMP, the dump only contains m out of n pages of physical memory
If SDA displays either of these error messages, you cannot analyze the crash
dump, but must take steps to ensure that any subsequent dump can be preserved.
To do this, you must increase the size of the dump file, as indicated in Section 1.1,
or adjust the system DUMPSTYLE parameter, as discussed in Section 1.1.2.
Under certain conditions, the system might not save some memory locations in
the system dump file. For instance, during halt/restart bugchecks, the system
does not preserve the contents of general registers. If such a bugcheck occurs,
SDA indicates in the SHOW CRASH display that the contents of the registers
were destroyed. Additionally, if a bugcheck occurs during system initialization,
the contents of the register display might be unreliable. The symptom of such
a bugcheck is a SHOW SUMMARY display that shows no processes or only the
swapper process.
Also, if you use an SDA command to access a virtual address that has no
corresponding physical address, SDA displays the following error message:
%SDA-E-NOTINPHYS, ’location’ not in physical memory
When you analyze a subset dump file, if you use an SDA command to access a
virtual address that has a corresponding physical address but was not saved in
the dump file, SDA displays the following error message:
%SDA-E-MEMNOTSVD, memory not saved in the dump file
SDA–9