Using the Logger › Size the Log Streams › Sizing Table for the Offload Data Sets

Sizing Table for the Offload Data Sets

The data contained within each log stream can be different. The differences include average record size and the rate at which data is written to the log.

The following is a sample sizing table:

RetPd Days

Specifies the retention period is the number-of-days worth of data to maintain within the log stream.

Formula variable: RetPd

Avg Rec Length

Specifies the average length of a record as it exists within the physical log stream. The records are maintained in a compressed format with the log stream.

Formula variable: Size

Hourly Count

Specifies the average number of records written to the log in a period of one hour.

Formula variable: Count

Total Byte Requirement

Specifies the total amount of storage in bytes required to maintain the desired amount of data.

Formula variable: Bytes

Example: Bytes = Size * ( Count * 24 ) * RetPd

Max Dsns

Specifies the maximum number of offload data sets that you want to be used to maintain the desired amount of data.

The System Logger allocates up to 168 offload data sets. No parameter exists that limits the number of offload data sets created. Therefore, use the number of offload data sets in your equation to help determine the size of a single offload data set. The more offload data sets that are used reduces the size requirement of a single offload data set. This equation is a balancing act. Offload data sets are allocated on a DASD device as a single extent. If the size is too large, you have trouble finding free space.

For log streams with a high volume of data, size the offload data set to maintain data for a single day or less in one offload data set.

Formula variable: Dsns

4K Blocks

Specifies the number of 4-KB blocks to allocate for a single offload data set.

The System Logger allocates the offload data sets based on the number of 4-KB blocks specified through the LS_SIZE parameter on the log stream definition. Select a size capable of holding at least 10 offloads worth of data. This size is dependent on the volume of data being written to the log stream.

Formula variable: LS_SIZE

Example: LS_SIZE = ( Bytes / 4096 ) / Dsns

Cyls

Specifies the number of cylinders on a 3390 DASD device required to allocate the offload data set based on the specified number of 4-KB blocks.

The System Logger does not use this value. This number is here as a reference point. The number of cylinders represented is for one offload data set.

Formula variable: Cyls

Example: Cyls = ( LS_SIZE * 4096 ) / 712140