Overview

This chapter introduces the Interval Monitor. During an Interval Monitor session, use the windowing commands and control keys described in Introduction to Performance Monitor, to manipulate your screen displays. The Interval Monitor provides additional commands that are described later in this chapter.

What the Interval Monitor Does

The Interval Monitor captures system-wide wait-time statistics and information related to wait-time statistics for each interval. An interval is a unit of time (30 minutes, 60 minutes, etc.). The time spanned by each interval is established by the system administrator, as is the total number of intervals to be maintained.

For example, you may want to maintain statistics based on 60-minute intervals and to store up to 24 intervals (one day of data). Once the day (24 intervals, in this case) elapses, the system wraps back and begins overwriting the earliest intervals with new information. For more information about system installation and setup, see the CA IDMS Performance Monitor System Administration Guide.

The first interval recorded after system startup will end at the next time-of-day which is a multiple of the Size of Interval setting. For example, if the system started at 01:03:00 and the Size of Interval setting is 10, the first interval will end at 01:10:00. To find the Size of Interval setting, see Options in Effect.

Note: In addition to online interval monitoring, there is also a batch component that allows you to report by interval and category. For more information, see the CA IDMS Performance Monitor System Administration Guide.

Problem-Solving

This chapter also provides information that you can use to help alleviate problems detected by using the Interval Monitor. If you detect a problem with your system, perform the following steps:

Try to isolate the applications that are heavy users of the problem resource. For example, storage-pool problems can be caused by an application that neglects to release acquired storage.
If Step 1 fails to correct the problem, increase the availability of the resource. For example, to solve storage-pool problems, you may need to expand the storage pool.

Uses and Users

The Interval Monitor is typically used by DBAs and DCAs to identify trends in system-resource utilization.

The Interval Monitor maintains statistics for several categories of information:

Db-key/area
I/O
Area
Buffer
Journal
Storage
Storage type
Program pool
Program loads
Log
Scratch
Queue
Message
Line I/O
Transaction
CDMSLIB libraries
SQL
Sysplex menu

The Interval Monitor automatically captures the appropriate wait information for each category. You can view this information either in detail or history form.

Note that the Interval Monitor maintains statistics separately for system and nonsystem data.

Area Name	Description
DDLDML	DC/UCF system definitions, maps, dialogs, source modules, and record descriptions
DDLDCRUN/ DDLDCQUE	Queue area
DDLDCSCR	Scratch area
DDLDCMSG	Message area
DDLDCLOG	Log area
DDLDCLOD	Load modules associated with DDLDML
DDLCAT	Physical database definitions (segments, database name tables, DMCLs); also contains SQL entity definitions at sites having the SQL option
DDLCATX	Indexes associated with DDLCAT
DDLCATLOD	Load modules associated with DDLCAT; also contains access modules at sites having the SQL option
DDLSEC	System user catalog area

Types of Interval Monitor Screens

The types of screens shown in the following table are available through the Interval Monitor and are used to display the statistics:

Screen	Description
Summary Detail screen	Provides wait statistics for each category
Summary History screen	Shows the average wait time for each interval in a graph
Wait Type by Interval screen	Summarizes wait information by category for a specific time interval. The screen displays this information both numerically and graphically. The Interval Monitor uses 1 of 4 scales for the graph, depending on the highest average wait time value: 0 - 1 second 0 - 5 seconds 0 - 10 seconds 0 - 50 seconds For values that exceed the scale of the graph, the Interval Monitor displays this symbol: =>.
Detail screens	Break down the wait activity for a particular category and interval. Where appropriate, these screens include other related statistics to help evaluate the use of resources and the cause of the waits.
History screens	Summarize the wait activity for a specific category, across all intervals. For each interval, these screens show the average wait time. The average wait time is displayed numerically and graphically. The Interval Monitor displays 1 of 4 scales for the graph, based on the highest average wait time value (see the ranges listed under Wait Type by Interval screen).

Screen Access Sequence

Typically, you access Interval monitor screens in this sequence:

Summary History screen—Use this screen to determine which interval experienced a high average wait time.
Wait Type by Interval screen—Use this screen to determine what types of waits occurred for the interval. Expect high values for I/O operations.
Specific detail screens—Use the specific detail screens to determine why waits occurred during a particular interval.