Transport Blocks environment variables in DataStage®

The following environment variables are all concerned with the block size (in bytes) used for the internal transfer of data as jobs run. Some of the settings only apply to fixed length records.

The following variables are used only for fixed-length records:

  • APT_MIN_TRANSPORT_BLOCK_SIZE
  • APT_MAX_TRANSPORT_BLOCK_SIZE
  • APT_DEFAULT_TRANSPORT_BLOCK_SIZE
  • APT_LATENCY_COEFFICIENT

APT_AUTO_TRANSPORT_BLOCK_SIZE environment variable in DataStage

Set the APT_AUTO_TRANSPORT_BLOCK_SIZE environment variable so that the framework calculates the block size for transferring data between players.

APT_LATENCY_COEFFICIENT environment variable in DataStage

Set the APT_LATENCY_COEFFICIENT environment variable to specify the number of writes to a block that transfers data between players.

Set the APT_LATENCY_COEFFICIENT environment variable to control the latency of data flow through a step. The default value is 5. Specify a value of 0 to transport a record immediately. This method is only used for fixed-length records.

Note: Many operators have a built-in latency and are not affected by this variable.

APT_DEFAULT_TRANSPORT_BLOCK_SIZE

Set the APT_DEFAULT_TRANSPORT_BLOCK_SIZE environment variable to specify the default block size for transferring data between players.

The APT_DEFAULT_TRANSPORT_BLOCK_SIZE environment variable is provided as part of the support for processing records longer than 128 KB.

Set a value for the APT_DEFAULT_TRANSPORT_BLOCK_SIZE environment variable in the range 8192 - 268435456 bytes (256 MB). If necessary, the value is rounded to the nearest page size for the operating size.

The default value is 131072 bytes.

APT_MAX_TRANSPORT_BLOCK_SIZE and APT_MIN_TRANSPORT_BLOCK_SIZE environment variable in DataStage

Set the APT_MAX_TRANSPORT_BLOCK_SIZE and APT_MIN_TRANSPORT_BLOCK_SIZE environment variables to specify the minimum and maximum allowable block size for transferring data between players.

APT_MIN_TRANSPORT_BLOCK_SIZE cannot be less than 8192 bytes, which is its default value. APT_MAX_TRANSPORT_BLOCK_SIZE cannot be greater than 1048576, which is its default value. These variables are only meaningful when used in combination with APT_LATENCY_COEFFICIENT.