gtpm6m14 | Main Supervisor Reference |
A channel check is an error associated with the channel subsystem, or the devices attached to it, that is reported in the interrupt response block (IRB) by the Test Subchannel (TSCH) instruction. There are 3 channel check conditions:
See ESA/390 Principles of Operation for more information about channel check conditions.
TPF handles channel checks by logging them on the RTA or RTL tape and tracking how often they occur. The channel check handler (CNCEX1) issues message CNCE0001E and cycles down the TPF system when the fault-rate threshold is exceeded. IFCCs are not tracked because they originate outside of the channel subsystem; tracking them would allow a defective device to cause TPF to automatically cycle down.
The channel check threshold is defined in subroutine EFL000 of segment CMKH of CSECT CCMCKH.