Delta and interval records

This section defines the differences among various DB2 Statistics counters, such as accumulated values, snapshot values, and high water mark values.

When a DB2 Statistics trace is active, DB2 maintains various Statistics counters and externalizes these counters at regular intervals. The main body of Statistics data is shown in IFCIDs 1 and 2. Although there is a small difference in their timestamps, you can assume that these IFCID are externalized simultaneously. These two records are called a DB2 Statistics record pair.

Other statistics information is shown in IFCID 199 (buffer pool statistics at data set level), IFCID 225 (DB2 storage statistics), and IFCID 369 (aggregated accounting statistics).

The counters provided in a DB2 Statistics record pair represent the DB2 activity between the time the pair is externalized and the time the Db2 system was last started. A counter is provided in one of the following forms:

• As an accumulated value since the Db2 system was last started. For example, the total number of SELECT statements that were executed since the system was last started.
• As a current or snapshot value. For example, the number of open data sets at the time the DB2 Statistics record pair was externalized.
• As a maximum or high water mark value the counter has reached since the time the system was last started. For example, the maximum number of open data sets at any time since the system was last started.

The Statistics report set does not report individual DB2 Statistics record pairs (for that purpose use the long Record Trace report). Instead, it calculates deltas between two consecutive DB2 Statistics record pairs and externalizes the delta records in Statistics traces and File data sets. It also uniformly distributes the delta records over user-specified intervals and externalizes the interval records in Statistics reports and Save data sets.