Disk I/O environment variables in DataStage

For systems where small to medium bursts of I/O are not desirable, the default 1 MB write to disk chunk size might be too small. The APT_BUFFER_DISK_WRITE_INCREMENT environment variable controls this size and can be set larger than 1048576 (1 MB). The setting must not exceed max_memory * 2/3.

The APT_EXPORT_FLUSH_COUNT environment variable enables the export operator to flush data to disk more often than it typically does (data is explicitly flushed at the end of a job, although the OS might choose to do so more frequently). Set this variable to an integer, which, in number of records, controls how often flushes are to occur. Setting this value to a low number (such as 1) is useful for real-time applications, but can cause a small performance decrease.

In many cases memory-mapped I/O contributes to improved performance. However, in certain situations such as a remote disk mounted by way of Network File System (NFS), memory-mapped I/O might cause significant performance problems. Setting the environment variables APT_IO_NOMAP and APT_BUFFERIO_NOMAP to "true" turns off this feature and sometimes affects performance.

AIX® and HP-UX default to NOMAP. Setting APT_IO_MAP and APT_BUFFERIO_MAP to "true" can be used to turn on memory-mapped I/O for these platforms.

The default value for APT_PHYSICAL_DATASET_BLOCK_SIZE is 128 KB.