Overview Screen [ ALLBASE/SQL Performance and Monitoring Guidelines ] MPE/iX 5.0 Documentation
ALLBASE/SQL Performance and Monitoring Guidelines
Overview Screen
This screen displays important aspects of the DBEnvironment's
performance, such as the data buffer pool miss rate and the amount of
available runtime control block space.
Click here to view figure.
To invoke the Overview screen, enter the o command from the Overview
subsystem or the /o command from other subsystems.
Field Definitions
REFRESH The screen refresh rate, in seconds.
SESSIONS The number of DBEnvironment sessions.
MAX XACT A scale showing the number of transactions that can be
active at one time. The maximum appears at the far
right of the scale, and the first three numbers on the
scale are 1/4, 1/2, and 3/4 of the maximum.
ACTIVE XACT The number of transactions that have started but have
not terminated (that is, a BEGIN WORK statement has
completed but a COMMIT WORK statement has not yet
begun.)
IMPEDE XACT The number of active transactions that are blocked
because they are waiting for a lock owned by another
session. To determine the amount of lock contention,
compare the IMPEDE XACT value with the ACTIVE XACT and
SESSIONS values.
DATA BUFFER The percentage of pages
MISS RATE that are not in the data buffer pool at request time.
The operating system must fetch these pages, either from
the operating system buffer pool or by a physical disk
read.
LOCK WAIT % The percentage of lock requests postponed because
another
session held an incompatible lock.
RUNTIME CB % The percentage of runtime control block space that is
occupied, calculated as follows:
RUNTIME CB % = (Used Pages / Max Pages) * 100
Each runtime control block page holds 4096 bytes. Lock
management is the single greatest user of runtime
control block space.
Used Pages The number of runtime control block pages in use.
Max Pages The maximum number of runtime control block pages. The
ControlBlockPages parameter that you specify in the
START DBE, START DBE NEW, or START DBE NEWLOG statements
is used to calculate MAX PAGES. MAX PAGES is usually
smaller than ControlBlockPages, and if ControlBlockPages
is too small, MAX PAGES is set to a certain minimum
value.
LOG FULL % The percentage of log file space that is occupied, as
calculated by the following formula:
LOG FULL % = (Used LgPgs / Max LgPgs ) * 100
A log page contains 512 bytes.
Used LgPgs The number of log pages that have been written.
Max LgPgs The maximum number of log pages. To change this value,
issue either the SQL START DBE or the SQLUtil ALTDBE
command.
Archive Mode Either ON or OFF, to indicate archive or nonarchive
logging.
LOG ERRORS The entire LOG ERRORS bar is displayed in inverse video
whenever an internal log counter is set to a nonzero
value. Two internal log counters are used, one for each
log file. With single logging, the log file is corrupt
if a log error occurs. With dual logging, the logs are
corrupt only if errors occur when writing to both log
files. To prevent data loss, you should immediately
store the DBEnvironment whenever a log error is
encountered.
Display Conventions
The numbers listed on the right side of the screen are also represented
graphically with half-brightness inverse video bars. The exclamation
point represents activity that has occurred during the most recent
refresh interval.
Related SET Commands
Use the SET REFRESH command to modify the refresh rate of the screen.
MPE/iX 5.0 Documentation
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