DB2 Server for VSE & VM: Operation
VMDSS contains a set of internal counters that are primarily
intended for IBM's use. However, if you have a good understanding
of the CP Macros that control data spaces within VM/ESA, you may find the
following counters useful.
- ESASEG
- The number of data space segments mapped. Data spaces are divided
into 256-page chunks called segments. A segment is mapped the first
time the database manager references a dbspace page that lies in that segment
(the first time it references a dbspace, the database manager decides where in
the data space the page will be). Mapping a segment consists of
defining a mapping between every dbspace page in that segment and its place on
disk. Empty pages are not mapped (because there is no disk page
allocated for an empty page). Even if all the dbspace pages in a data
space segment are empty, the database manager still marks that segment as
mapped and increments ESASEG.
- MAPSEGPG
- The number of calls to CP's MAPMDISK DEFINE macro to map the above
ESASEG segments. It may take 0 (all pages empty) or many DEFINEs per
segment, because one DEFINE can only work on a contiguous set of data space
pages and database manager must skip empty pages.
- REQMAPPG
- The number of requests to remap a page. When the database manager
gets a new disk page for a dbspace page (either when database manager shadows
it or starts using a previously empty dbspace page), it must redefine the data
space mapping for that page to point to the new disk location.
- MAPPG
- The number of MAPMDISK DEFINE macro calls done to satisfy the REQMAPPG
requests above. The database manager tries to delay the requests as
long as possible in order to group as many as it can into one DEFINE.
In the worst case, there will be 1 DEFINE for every request. In the
best case, 1 for every 256 requests.
- SAVESLD
- The number of calls to CP's MAPMDISK SAVE macro to save the contents
of a page in the Data Space on DASD.
- SAVEMXRN
- The sum of "maximum runs". Before issuing a MAPMDISK SAVE
macro for one or more blocks of 32 pages, a maximum run is computed. It
is the largest number of contiguous blocks of 32 pages that are being
saved. SAVEMXRN is an indicator of whether the blocks of pages being
saved are consecutively modified (during a dataload for example) and
determines the span length to use for the REFPAGE macro following completion
of MAPMDISK SAVE macro (refer to SCBLKREF and SCSPNREF).
- SAVEBLK
- The number of 32 page blocks for which CP's MAPMDISK SAVE macro was
issued. The MAPMDISK SAVE macro is issued for modified blocks of pages
at checkpoints and when the number of modified blocks reaches the SAVEINTV
threshold.
- WAITSLD
- The number of times the database manager was forced to wait for a MAPMDISK
SAVE macro to save modified pages on DASD. To ensure that all modified
data is safely stored on DASD, the checkpoint processing cannot finish until
all outstanding MAPMDISK SAVE requests are complete.
- REFBLOCK
- The number of times a block form of CP's REFPAGE macro was issued
telling CP the reference pattern for a group of pages.
- REFBPAGE
- The number of pages for which a block form of REFPAGE macro was
issued.
- REFBSPAN
- The sum of spans used in block form of REFPAGE macro.
- REFLST
- The number of times a list form of CP's REFPAGE macro was
issued.
- REFLPAGE
- The number of pages for which a list form of REFPAGE macro was
issued.
- DIAG10
- The number of DIAGNOSE X'10' instructions processed that release
the main or expanded storage back to CP.
- DIAG10PG
- The number of data space pages that have been released using the DIAGNOSE
X'10' instruction.
- SCDIAG10
- The number of blocks of 32 pages for which storage has been released
following the completion of MAPMDISK SAVE request.
- SCREF
- The number of blocks of 32 pages for which a reference pattern was
established following the completion of MAPMDISK SAVE request.
- SCBLKREF
- The number of times a block form of the REFPAGE macro was issued following
the completion of MAPMDISK SAVE request.
- SCSPNREF
- The sum of spans used in the block form of the REFPAGE macro following the
completion of the MAPMDISK SAVE request. The size of each span is based
on the largest number of consecutive blocks of 32 pages that were (SAVEMXRN
counter). As the number of consecutively modified blocks increases
(during a dataload for example) the size of the span given to CP's
REFPAGE macro also increases.
- SAVEGNRL
- The number of save requests made by general agents when the SAVEINTV has
been reached for a data space.
- SAVECHK0
- The number of save requests made by the checkpoint agent to flush the page
buffers prior to starting checkpoint processing.
- SAVECHK1
- The number of save requests made by the checkpoint agent during checkpoint
processing.
To display the counters, type the following at the operator console:
COUNTER INTERNAL *
For example:
+--------------------------------------------------------------------------------+
| counter internal * |
|Counter values at DATE='07-23-91' TIME='08:57:51' |
| ESASEG 429 |
| MAPSEGPG 432 |
| REQMAPPG 15 |
| MAPPG 13 |
| SAVESLD 1 |
| SAVEMXRN 1 |
| SAVEBLK 1 |
| WAITSLD 0 |
| REFBLOCK 860 |
| REFBPAGE 163912 |
| REFBSPAN 68485 |
| REFLST 1580 |
| REFLPAGE 101120 |
| DIAG10 1580 |
| DIAG10PG 101120 |
| SCDIAG10 0 |
| SCREF 0 |
| SCBLKREF 0 |
| SCSPNREF 0 |
| SAVEGNRL 0 |
| SAVECHK0 0 |
| SAVECHK1 0 |
| ARI0065I Operator command processing is complete. |
+--------------------------------------------------------------------------------+
To reset the counters to zero, type the following:
RESET INTERNAL *
For example:
+--------------------------------------------------------------------------------+
|reset internal * |
|Counters reset at DATE='05-23-91' TIME='09:26:15'. |
|counter internal * |
|Counter values at DATE='07-23-91' TIME='09:26:51' |
| ESASEG 0 |
| MAPSEGPG 0 |
| REQMAPPG 0 |
| MAPPG 0 |
| SAVESLD 0 |
| SAVEMXRN 0 |
| SAVEBLK 0 |
| WAITSLD 0 |
| REFBLOCK 0 |
| REFBPAGE 0 |
| REFBSPAN 0 |
| REFLST 0 |
| REFLPAGE 0 |
| DIAG10 0 |
| DIAG10PG 0 |
| SCDIAG10 0 |
| SCREF 0 |
| SCBLKREF 0 |
| SCSPNREF 0 |
| SAVEGNRL 0 |
| SAVECHK0 0 |
| SAVECHK1 0 |
| ARI0065I Operator command processing is complete. |
+--------------------------------------------------------------------------------+
[ Top of Page | Previous Page | Next Page | Table of Contents | Index ]