Data set management modes

Review the data set management modes available for PDS V2.

When collecting historical data using PDS V2, you have the option to manage the data sets by space or by time. The specification of the mode depends on the Extent Constraint Removal (ECR) attribute of the SMS data class used when allocating the data sets.

Space-based (Extent Constraint Removal = NO)

The amount of historical data in each data set depends on the size of the data set. The number and size of the data sets allocated are defined using parameters Kpp_PDS2_FILE_COUNT and Kpp_PDS2_STORE_SIZE. These data sets are online at all times. All the allocated data sets except for one are used for writing data, while one data set remains empty for future switches. The switch to the next data set occurs when the current data set runs out of space; no extents are taken when the current data set is full.

To use this mode, allocate the data set using an SMS data class that has the Extent Constraint Removal (ECR) parameter set to a value of NO. The data class can be assigned using the SMS data class ACS routine.

Note: It is recommended that you periodically review the data set sizes and change the size to fit your needs.

Time-based (Extent Constraint Removal = YES)

Each data set contains 24 hours of historical data. The number and size of the data sets allocated are defined using parameters Kpp_PDS2_FILE_COUNT, Kpp_PDS2_STORE_SIZE and Kpp_PDS2_SEC_SIZE. These data sets are online at all times. All the allocated data sets except for one are used for writing data, while one data set remains empty for future switches. The switch to the next data set occurs around local midnight.

When the current data set fills up and cannot be extended, recording rolls over to the next data set and less than 24 hours of data may be present in the data set. It is important that each PDS V2 data set be large enough to contain historical data for a full 24-hour period.

To use this mode, allocate the data set using an SMS data class that has the Extent Constraint Removal (ECR) parameter set to a value of YES. The data class can be assigned using the SMS data class ACS routine.

Note: With ECR=YES, it is possible that the data sets might grow significantly beyond their initial size. For this reason, it is recommended that time-based mode be used only when you need historical data for a fixed number of days.

For both time-based and space-based modes, a wraparound process is used to allocate and delete the data sets. When a switch occurs, the switch is made to the next empty data set. Then, in preparation for a future switch, the oldest data set is removed and replaced with a newly allocated, empty data set with the same name of the deleted data set. This process allows the opportunity to address problems that might occur when allocating the data set.

The number of PDS V2 data sets for historical data for a given agent at one time will never exceed the value defined in Kpp_PDS2_FILE_COUNT. In addition to the data sets for historical data, there is also a configuration data set that is allocated and online at all times for each agent.