Use Top diagnostic event triggers (-diagTopN) to specify the number of most prominent event triggers (offenders) causing a diagnostic event for which diagnostic data must be reported. This limited reporting functionality reduces the amount of data for the DBA to review yet provides enough diagnostic data to isolate the problem.

Operating system and syntax UNIX / Windows -diagTopN n
Use with Maximum value Minimum value Single-user default Multi-user default
Database Server 32000 0 – 0
n
An integer in the range of 0 to 32000, specifying the number of connections to be included in the data diagnostic report. The default value is set to 0, which indicates that the limited reporting functionality is disabled, and the diagnostic data is collected for all concurrent connections.
The -diagTopN startup parameter limits the diagnostic data reported for the following diagnostic events:

  • Lock table overflow (-diagEvent locktable)

  • BI threshold (-diagEvent bithold)

There is no distinct -diagTopN value for each of these two diagnostic events, and the same limiting value applies to both.

When a lock table overflow event is triggered at the Detailed Data event level, which generates detailed transaction information, -diagTopN limits reporting to connections that have top n lock table entries while also reporting detailed transaction information for those same connections. In this case, the -diagTopN parameter does not limit reporting to connections with just the top n longest-running (oldest) transactions. Therefore, -diagTopN collects detailed transaction information related to only the reported connections for the lock table overflow event, excluding transactions that were not involved in triggering that event.

Similarly, when a BI threshold event is triggered at the Detailed Data event level, which generates detailed lock table information, -diagTopN limits reporting to connections that have the top n longest-running transactions while also reporting detailed lock table information for those same connections. In this case, the -diagTopN parameter does not limit reporting to connections with just top n lock table entries. Therefore, -diagTopN collects detailed lock table information related to only the reported connections for the BI threshold event, excluding transactions that were not involved in triggering that event.
Note:
  • When the BI threshold diagnostic event is triggered at the Detailed Data event level, the -diagTopN parameter reports diagnostic data for the top n longest-running transactions to the diagEvent_transaction_detail file. For more information on the files created by diagnostic data collection, see Data Files.
  • Not all transactions involve a connected user. For example, JTA transactions that are re-established during database startup do not have an active database connection.
To change the -diagTopN parameter while the database is running, you can use the following options: