HP 3000 Manuals

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.


            

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