──/1\─POPULATIONWARN─ = ┬─<1-99>─┬──────────────────┬┬───────┤
│ └( ─┬DISPLAY──┬─ ) ┘│
│ └NODISPLAY┘ │
└───────── 0 ────────────────┘ Use this option to have the Enterprise Database Server issue a notification when a data set reaches a percentage of its allowed population. (The population calculations are based on areas.) Notification is placed in the control file and, by default, is also sent to the operator display terminal (ODT) in the form of a task that is placed in the waiting mix.
This option cannot be specified for the global data set.
In general, knowing when structures are approaching their population limit enables steps to be taken to avoid having applications receive limit errors and to avoid the resulting unplanned database downtime.
The POPULATIONWARN option is off by default. That is, the control file is not updated and no notifications are issued.
The value for POPULATIONWARN can also be changed dynamically while the database is running by using the POPULATIONWARN Visible DBS command.
If you decide to change the value for POPULATIONWARN by way of a DASDL update after you change the value by using the STRUCTURE CHANGE POPULATIONWARN Visible DBS command, you must perform a control file override. The override enables the system to recognize that the DASDL update value takes precedence over the value you specified with the Visible DBS command.
For additional information about the POPULATIONWARN Visible DBS command or the DMCONTROL OVERRIDE POPULATIONWARN option, refer to the Enterprise Database Server Utilities Operations Guide.
The following parameters are available for use with the POPULATIONWARN option:
|
Parameter |
Explanation |
|---|---|
|
0 |
Switches off the option. To explicitly turn off the POPULATIONWARN option, include the following statement in the database DASDL source file: POPULATIONWARN = 0 |
|
1–99 |
Specifies the percentage of total structure capacity that triggers a warning message. The percentage is expressed as an integer. For instance, to trigger a warning when a structure is 85 percent full, include the following statement in the database DASDL source file: POPULATIONWARN = 85 |
|
(DISPLAY) |
Updates the control file and enables the delivery of a warning message when a structure reaches its warning level capacity. DISPLAY is the default. For instance, if the following statement is included in the database DASDL source file, the control file is updated and a warning message is issued when a structure becomes 75 percent full: POPULATIONWARN = 75 (DISPLAY) |
|
(NODISPLAY) |
Updates the control file only. The warning message is not sent. For instance, if the following statement is included in the database DASDL source file, the control file is updated, but a warning message is not issued when a structure becomes 75 percent full: POPULATIONWARN = 75 (NODISPLAY) |
| Note: | The total structure capacity might be different from that specified in the database DASDL source file if automatic population increases have occurred because of the use of the POPULATIONINCR option. |
The POPULATIONWARN option can be used at both the database and the structure level. Specifications applied at the structure level take precedence over those at the database level.
When the designated percentage of total structure capacity is reached
-
The control file is updated to reflect the time of the event.
-
Unless the NODISPLAY switch is set, a message similar to the following is sent to the ODT in the form of a task that is placed in the waiting mix:
MYDB: WARNING - CUSTOMERS have reached 85% of its capacity of 750 rows.
Use the IB (Instruction Block) system command to display the text of the message.
Once the warning condition for a structure has been met—even if automatic population increases occur—further warnings are not issued for that structure until the related control file information has been reset.
To reset the control file information for a structure, perform either a
-
DASDL UPDATE to increase the allowed number of areas
-
Reorganization or garbage collection that reduces the number of in-use areas (ROWSINUSE) below the target percentage
The actual number of records that can be stored within a structure is based upon the number of areas designated for the structure and the structure type. For instance, the record calculation for
-
Variable‑format data sets is based on the maximum allowed record size
-
Compact data sets is based on the average record size
Therefore, even if a population is specified, the actual run-time evaluation of the allowed number of records might differ from the specified number. This effect is particularly noticeable when the specified population is small compared to the number of records that can be contained in an area.
