Performance Considerations

This section contains questions for system programmers to answer when planning for the channel-attachment configuration and for Advanced Function Presentation^(TM) licensed programs.

• How much and what kind of data will be printed?

  A printed page can consist of different types of text, images, overlays, and fonts. The combination of information on the page determines the time needed to prepare the data for printing. Jobs with little text and no image or graphics are processed faster than jobs with complex pages that may include scaling and image decompression.

• Will multiple pages of data be printed per sheet?

  If an application uses N-Up Page Positioning or Cut Sheet Emulation (CSE), you will be increasing the number of pages printed per minute. For example, for a printer with a maximum throughput of 229 simplex 8.5 in. forms per minute, changing the application to print 2-Up 11 in. forms increases the maximum throughput to 354 simplex pages per minute. If the application is duplex, the maximum throughput is doubled to 708 pages per minute.

  Increasing the throughput increases the amount of data per minute being transferred to and processed by the system and the printer. System and channel loads may need to be reevaluated and adjusted to allow for the increased processing and transfer requirements. Increasing the number of pages per minute also intensifies processing based on page count, such as Checkpointing. Consider increasing the Check Point interval for applications using N-Up, CSE, or duplexing.

• How busy is the system?

  Several things affect the performance of the system and directly affect communication with the printer:

  • Speed of the computer system
  • Amount of available storage
  • Importance of tasks assigned in the system
  • Control program used to drive the printer
• Can the attachment support the data rate required for this application?

  Slower technologies such as S/370 Parallel channel and Token Ring are not recommended for applications that are data intensive and require a high bandwidth. Newer technologies such as FICON channel or Gigabit Ethernet provide excellent bandwidth and room for future growth in print data.

  Plan your system so that it can adjust to the change and growth of your company.

Consider the following issues while setting up your channel-attachment configuration.

System/370 Attachment

• Transfer rates in DC Interlock mode have a greater reduction as cable distance increases than does Data-Streaming mode.
  Note:
  For best performance, use data-streaming mode.
• Different processor channels have different rates of transfer depending on the channel number. Refer to the system reference manual for your host system for data-transfer rates. Not all channels support data-streaming mode.
• Set the missing-interrupt handler (MIH) for 13 minutes or more.
• When attached to an IBM^(R) 3044-II Fiber Optic Channel Extender or an IBM 9034 ESCON^(R) Converter, configure the printer for one of the data-streaming transfer modes and not the DC Interlock transfer mode.
  Note:
  An exception to the above is when XDF is used in the interface with the distance between the host and the printer exceeding 10 km, then use the DC Interlock transfer mode. See Note 2 in Figure 22.
  For any 3044-II restrictions on transfer rate, refer to the 3044-II publications.
• Using data chaining with data-streaming mode can cause an overrun condition. For more details, see the channel or system library publication for your computer system, and System/370^(TM) Principles of Operation. (IBM PSF does not use data chaining.)
• Before attaching the printer to non-IBM equipment (such as channel extenders), ensure that the equipment supports the printer. The equipment vendor can answer your questions about configuration options and other channel-attachment issues.

ESCON Attachment

The ESCON channel is the replacement for the System/370 parallel channel. It provides improvements in data rate, physical path length, cable space requirements, and overall system connectivity.

Set the missing-interrupt handler (MIH) for 13 minutes or more.

FICON Attachment

The FICON^(TM) channel is the high performance replacement for the System/370 parallel channel and the ESCON channel. It provides improvements in data rate, physical path length, cable space requirements, and overall system connectivity.

Set the missing-interrupt handler (MIH) for 15 minutes or more.