Channel Analysis

Specifics - Channel Analysis:

There have been many upgrades to channels over the years. From Escon to Ficon to the new z/17 architecture, each upgrade has improved the performance of transfering data. The I/O Processor (IOP) was added to manage I/O operations, thus giving more processing power back to the CPU to improve overall performance. These IOPs are called Data Processing Units (DPU). Both on the new Telum chip, the System Assist Processor (SAP) is a processor core(s) and the DPU is a low-latency silicon-level accelerator engine(s) - usually there are mutliple of both. Currently the only adapter using the SAP is a Ficon Express adapter in Ficon mode. SAPs share workload, acting as one giant processor, DPUs do not.

The z17 introduced many changes to the channel environment. The following presentation covering these changes: Introduction to z17 Channel Performance Management

Helpful ESAMON screens/ESAMAP reports:

ESACHAN - Shows the channel performance

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  • Pct Channel Utilization - This shows the channel utilization for the LPAR and all the LPARS to which it is connected. If the channel utilization is over 30%, consider faster channels or moving data. If the total utilization for all of the connected LPARS is over 40%, consider adding channels, moving to faster channels or moving data to other channels. Alerts should be set for these percentages.
  • Data Unit Pct/Work Unit Pct - This shows the percent busy for the channel. This should really stay under 40%. Again, alerts can be set for these. The Total Reads and Writes per second shows the total for the CEC so only one LPAR on each CEC needs to provide the information.
  • DPU Util Pct - This shows statistics for the new Data Processing Units (DPUs). Only will show if the channel is using the new FICON Express 32-4P or the Network Express adapters.Like the SAPs, smaller I/O block sizes will impact performance. Heavy use of non-zHPF operations on a FICON Express 32-4P card will also impact DPU performance and will show up as high DPU utilization. Watch for any single overutilized DPU as they are not shared like SAPs.
  • DPU Num - This shows the DPU number. Each channel is associated with one DPU (they don't work together like SAPs)
  • Note: This report can be used to verify issues such as mixing ESCON and FICON channels or a channel being overworked. Also, for DPUs, channel utilization per DPU and DPU utilization per channel can both be seen.
    • ESACHNH - Shows the HiperSocket channel performance

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  • Channel Type - This shows the type of channel.
  • Messages Sent/Sec LPAR/TOTAL - This shows the number of messages sent per second on this path (LPAR) and on this path for all LPARs (TOTAL). This can be viewed to track message volume trends.
  • DataUnits Sent/Sec LPAR/Total - This shows the number of data units sent per second on this path (LPAR) and on this path for all LPARs (Total). This can be viewed to track message volume trends.
  • Failed Send/Sec - This shows unsuccessful attempts to send messages. Watch for errors.
  • Failed Receives Unavail Buffers LPAR/Total - This shows the number of times transmissions failed due to unavailable receive buffers for this LPAR (LPAR) and for all LPARs (Total). Watch for errors.
    • ESAIOP - Shows the I/O processor unit performance

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  • I/O Proc Nmbr - This shows the processor number (and how many SAPs there are). Since SAPs share the workload, high utilization will be seen across all SAPs.
  • I/O Processor Pct Busy - This shows the I/O processor utilization. If high, it may indicate a problem, especially if there is high Pend time from ESADSD2.
  • Percent of Strts busy - This shows the percentage of SSCH busy time in each step of the process.
  • Note: Small block sizes and a large number of FICON Express adapters in Ficon mode will add to high SAP utilization.
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