DCMT DISPLAY TRACE Command

The DCMT DISPLAY TRACE command displays the tracing options currently in effect for your system.
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The DCMT DISPLAY TRACE command displays the tracing options currently in effect for your system.
This article describes the following information:
2
Syntax
The following diagram shows the syntax for the DCMT DISPLAY TRACE command:
►►─ DCMT ─┬───────────────────┬─ Display TRACe ───────────────────────►◄           └─ broadcast-parms ─┘
Parameter
  • broadcast-parms
    Executes the DCMT command on all or a list of data sharing group members. For more information about broadcasting and broadcast-parms syntax, see Using System Tasks.
Example
The following example illustrates the output from a DCMT DISPLAY TRACE command when trace information is not being saved.
DCMT DISPLAY TRACE System tracing (SYSTRACE):     ON             Trace table size:    20 MB          Address: 39A40000           Adjunct table size:    10 MB          Address: 36603000 Save: OFF          Driver: INACTIVE             Area: DDLDCLOG
 
The following example illustrates the output from a DCMT DISPLAY TRACE command when trace information is being saved to a DDLDCTRC area.
DCMT DISPLAY TRACE System tracing (SYSTRACE):    ON          Trace table size:     4 KB        Address: 39B65000        Adjunct table size:     8 MB (S)    Address: 36603000    Save: ON           Driver: ACTIVE             Area: DDLDCTRC     0% FULL  ------------Trace service driver statistics-------------- Driver started.................2009-12-08-12.23.21.151167 Number of save requests................................44 Number of times entries missed..........................2 Bytes/hour........................................1067733 Pages/hour............................................300 Number of reads........................................14 Number of writes........................................9 Number of read waits....................................1 Number of write waits...................................0 Number of page range resets.............................1 Number of area full waits...............................0 Number of errors........................................0 % of waits to I/Os......................................0 Number of RUs...........................................8 Number of look aheads...................................5 % of look aheads to RUs................................63
  • System Tracing
    Potential values are as follows:
    • ON
      System tracing is enabled.
    • OFF
      System tracing is disabled.
  • Trace table size
    The size of the system trace table in kilobytes (KB) or megabytes (MB).
    If the characters “(S)” follow table size, it indicates that the contents of the system trace table are being saved.
  • Address
    The address of the system trace table.
  • Adjunct table size
    The size of the adjunct trace table in kilobytes (KB) or megabytes (MB).
    If the characters “(S)” follow table size, it indicates that the contents of the adjunct trace table are being saved.
  • Address
    The address of the adjunct trace table.
  • Save
    Potential values are as follows:
    • ON
      Trace saving is enabled.
    • OFF
      Trace saving is disabled.
    • REQUESTED
      Trace saving has been requested but is not yet fully enabled.
  • Driver
    Potential values are as follows:
    • ACTIVE
      Trace service driver is active.
    • INACTIVE
      Trace service driver is inactive.
    • PENDING
      Trace service driver is starting up.
  • Area
    Potential values are as follows:
    • DDLDCLOG
      Trace information is written to the log area.
    • DDLDCTRC
      Trace information is written to the trace area.
  • % Full
    The percentage of space used in the area.
  • Trace service driver statistics
    A header for statistics that are displayed only if trace saving is enabled.
  • Driver started
    The date and time at which the trace service driver was started.
  • Statistics reset
    The date and time when the driver statistics were reset due to overflow.
  • Number of save requests
    The number of requests made to save trace information.
  • Number of times entries missed
    The number of times one or more trace entries were not saved because they had been overlaid before they could be written.
  • Bytes/hour
    The rate at which trace information is being written, specified as bytes per hour.
  • Pages/hour
    The rate at which pages are written to the log or trace area, specified as pages per hour.
  • Number of reads
    The number of pages read from the log or trace area.
  • Number of writes
    The number of pages written to the log or trace area.
  • Number of read waits
    The number of times the driver had to wait for a read to complete.
  • Number of write waits
    The number of times the driver had to wait for a write to complete.
  • Number of page range resets
    The number of times the driver had to recalculate the range of pages into which it can write information.
  • Number of area full waits
    The number of times the driver had to wait for the contents of the log or trace area to be archived.
  • Number of errors
    The number of I/O errors encountered.
  • % of waits to I/Os
    The percent of waits to I/O requests.
  • Number of RUs
    The number of run units currently in use.
  • Number of look aheads
    The number of look ahead reads in effect.
  • % of look aheads to RUs
    The percent of run units being used for look ahead reads.
How to Reduce the Number of Missed Entries
Eliminating missed trace entries can be difficult; however, there are steps you can take to reduce the number of missed entries. In the trace information output, if the value for number of times entries missed is large compared to the value for number of save requests, consider taking one or more of the following actions:
  • Save trace information to the trace area rather than the log area.
  • Reduce the amount of trace information being saved. If only extended trace information is of interest, be sure to allocate an adjunct table so only extended trace information is saved.
  • Increase the size of the trace or adjunct table.
  • Ensure that the appropriate archive utility is executed often enough that the trace area does not fill. The easiest way to do this is to automate the submission of the archive job using a WTO exit.