The DO (Diagnostic Options) command displays, sets, or resets various diagnostic options. The system records all mainframe hardware errors in the system summary log (SUMLOG) and can report the errors in a mainframe hardware report. These options can result in logging additional information, altering error recovery behavior, and causing system stops.

Syntax

── DO ─┬─────────────────────┬───────────────────┤
       │       ┌◄─┬──────┬─┐ │
       │       │  └── , ─┘ │ │
       ├─ - ─┬─┴─┬─ CML ─┬─┴─┘
       └─ + ─┘   ├─ DCL ─┤
                 ├─ DRI ─┤
                 ├─ DSO ─┤
                 ├─ DUQ ─┤
                 ├─ IOD ─┤
                 ├─ LAE ─┤
                 ├─ RST ─┤
                 └─ SIG ─┘

Explanation

DO

Displays the options that are currently set.

DO + CML

Check Memory Links Option

When set, the MCP checks memory links as an extra diagnostic.

DO − CML

This is the default setting.

DO + DCL

Disable Comlink Option

When set, the MCP disables the Comlink interface. MCP partition state will transition from Running to Not Responding.

DO − DCL

This is the default setting.

DO + DRI

Do Not Reinitialize IOP Option

If an IOP fails when this option is set, the system does not attempt to reinitialize the IOP automatically. The system leaves the IOP out of service so that you can manually gather diagnostic information from it at a later time. Leaving the IOP out of service sometimes makes the system unusable.

DO − DRI

Diables the DRI option. This is the default setting.

DO + DSO

Dump on Stack Overflow Option

When set, triggers a memory dump when a process terminates with a stack overflow exception.

DO – DSO

Disables the DSO option. This is the default setting.

DO + DUQ

Dump Unit Q

When set, the MCP will take a non-fatal memory dump by UNIT Q ASSERT when the MCP determines that an I/O unit queue is in an inconsistent & non-operational state for more than 5 minutes. At most one UNIT Q ASSERT memory dump will be taken for any specific unit, and at most 2 UNIT Q ASSERT dumps will be taken overall. These counters are cleared by a halt/load.

DO – DUQ

Disables the DUQ option. This is the default setting.

DO + IOD

I/O Diag Deadstop Option

When set, selected I/O dumps result in a DEAD 20D error. You can then take state dumps and a force dump. If DEADSTOP handling has been disabled, you must manually take a state dump and a force dump.

DO − IOD

Disables the IOD option.

DO + LAE

Log All I/O Exceptions Option

When set, I/O exception log entries are made for exceptions that are not normally logged. This option is used for diagnosing peripheral problems.

DO − LAE

Sets the option to its default setting. The system only logs unexpected exceptions.

DO + RST

Resize Trace Option

When set, an internal MCP trace is turned on to track the number of array resizes being performed on the system. Use of this option can cause severe system performance degradation.

DO − RST

Is the default setting. The array resize trace is inactive.

DO + SIG

Codefile Verification Option

When set, diagnostic information is written when the MCP generates codefile verification data and when the MCP attempts to verify a codefile. This can be helpful in troubleshooting codefile verification errors.

DO − SIG

Is the default setting. The codefile verification option is inactive.