Most of the monitor requests covered in this chapter depend on periodic collection of data. When this collection process is disturbed, the returned data can temporarily become confusing or inaccurate.
If this happens, the user receives a warning message indicating that the data returned may not give a true picture of system or user activity.
The following are some common situations in which a warning message is provided:
For more detailed information on warning and error messages, see Messages.
Errors Resulting from PMPC Subsystem Failures
All MONITOR requests get their information from the PMPC subsystem. In the event of a PMPC internal software failure, the system will generate one of several possible errors. Each of these errors causes the PMPC subsystem to discontinue the current session to prevent the error from crashing the entire system.
If the system encounters such an error, it takes a snapshot dump and does one of the following:
Even though the PMPC subsystem may be partially or fully shut down due to an internal software error, the shut down avoids a crash and allows the system to process other types (non-PMPC) of requests. Although the system resources are cleaned up as much as possible after such an internal software error, there may be leftover resources or tasks that stay hung waiting on a response from the task that originally caused the error.
After encountering a PMPC subsystem internal failure, especially if a subsequent MONITOR request results in an error, the administrator should do a manual DBS restart as soon as possible (taking care not to unnecessarily disrupt users) to rid the system of task and resource fragments. The administrator should also report the snapshot dump and any related errors in the event log to the Teradata Support Center.