For optimal performance during cache partitioning for Aggregator, Joiner, Rank, and Sorter transformations, configure multiple cache directories for the Data Integration Service. For optimal performance when multiple threads write to a file target, configure multiple target directories for the Data Integration Service.
When multiple threads write to a single directory, the mapping might encounter a bottleneck due to input/output (I/O) contention. An I/O contention can occur when threads write data to the file system at the same time.
When you configure multiple directories, the Data Integration Service determines the output directory for each thread in a round-robin fashion. For example, you configure a flat file data object to use directoryA and directoryB as target directories. If the Data Integration Service uses four threads to write to the file target, the first and third writer threads write target files to directoryA. The second and fourth writer threads write target files to directoryB.
If the Data Integration Service does not use cache partitioning for transformations or does not use multiple threads to write to the target, the service writes the files to the first listed directory.
In the Administrator tool, you configure multiple cache and target directories by entering multiple directories separated by semicolons for the Data Integration Service execution properties. Configure the directories in the following execution properties:
Defines the cache directories for Aggregator, Joiner, and Rank transformations. By default, the transformations use the CacheDir system parameter to access the cache directory value defined for the Data Integration Service.
Defines the cache directories for Sorter transformations. By default, the Sorter transformation uses the TempDir system parameter to access the temporary directory value defined for the Data Integration Service.
Defines the target directories for flat file targets. By default, flat file targets use the TargetDir system parameter to access the target directory value defined for the Data Integration Service.
Instead of using the default system parameters, developers can configure multiple directories specific to the transformation or flat file data object in the Developer tool.
A Lookup transformation can only use a single cache directory.