page of GC20-t801-7 As Updated April 1, 1981 by TNL GN25-0829 IDENTIFYING AND LOCATING A PAGEABLE MODULE If a proqram check PSW or SVC PSi points to an address beyond the end of the CP resident nucleus, the failing module is a pageable module. The CP system load map identifies the end of the resident nucleus.
Go to the address indicated in the PSW. Backtrack to the beginning
of tggi paqe frame. The first eight bytes of that page frame (the page
frame containinq the address pointed to by the PSW) contains the name of
the first pageable module loaded into the page. If multiple modules
exist within the same page frame, identify the module using the load map
and failing address displacement within the page frame. In most cases, register 12 will point directly to the name. To locate a pageable module whose address 1S shown in the load map; use the system VMBLOK segment and page tables. For example, if the
address in the load map is 55000, use the segment and page tables to
locate the module at segment 5, page 5. VMDUMP RECORDS: FORMAT AND CONTENT When a user issues the VMDUMP command, CP dumps virtual storage of the
user's virtual machine. CP stores this dump on the reader spool file of
a virtual machine that the user specified as an operand on the VMDUMP command. CP writes the storage dump to the spool file as a series of logical
records. Each spool file record and each logical dump record is
4096-bytes long. However, because each spool file record contains a
header, one logical dump record does not fit into one spool file record.
For this reason, CP splits a logical dump record into two parts. CP writes one part to one spool file record and the other part to an
adjacent spool file record. The size of each part varies depending upon
the of space remaining in the spool file record that CP is
currently usinq. Thus, each logical dump record spans two spool file
records. Fiqure 10.1 shows the format of spool file records, the format
of loqical dump records, and how loqical dump records span spool file
The first spool file record contains a spool page buffer linkage
block (SPLINK) followed by a TAG area followed by dump information. All
other spool file records contain only a SPLINK followed by dump information. A SPLINK, which contains data needed to locate information in the
associated spool file record, has the following format:
hexadecimal Q!l§gi o
C lengih 4 bytes
4 bytes
4 bytes
4 bytes
the DASD location-(DCHR) of the next page
the DASD location (DCHR) of the previous
page buffer
binary zeros
the number of data records in the buffer Part 1. Debugging with VM/310 63
April 1, 1981
The TAG area contains either binary zeros or user supplied data. If
a virtual machine program or the user has issued the TAG command, the
TAG area contains the information provided via this command. Otherwise
it contains binary zeros.
The first logical dump record contains a dump file information record (DMPINREC). The second and third logical dump records each contain a
dump file key storage record, DMPKYREC1 and DMPKYREC2 respectively. The
dump file key storage records contain the value of the storage keys
assigned to each page of virtual storage. The remaining logical dump
records contain the virtual machine storage dump.
CP records the storage dump sequentially starting with the lowest
address dumped and ending with the highest address dumped. CP records
each byte as an untranslated 8-bit binary value.
For a description of the format and contents of DMPINREC, see nsi! an! Logic. For a description of DMPKYREC1 and DHPKYREC2, see DHPKYREC also in the natg gnd Logic­ publicat ion.
To locate a specific logical dump record, use the algorithm: 240+16n+4096n loc = --------------- 4096 where: n·is a number that identifies the dump record. For example, to
locate the first dump record, assign n a value of 1; to locate
the second record, assiqn a value of 2, and so forth. is the quotient and remainder of the algorithm. Together
these values specify a spool file record and an offset into that
record where logical dump record begins. The quotient
specifies the spool file record, and the remainder specifies the
offset into the spool file record.
The following example shows how to locate the third logical dump
record: 240+(16x3)+(4096x3) loc =
----------- 4096 12576
loc = 4096 quotient = 3
remainder = 288
Thus, the third dump record starts 288 bytes into the third spool file
record. 64 IBM VM/370 System programmer's Guide
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