To work around this issue, change the detection cycle to a value that is in the allowed range. By using Group Policy, you can manipulate the time between each detection cycle from 1 hour to 22 hours. For example, if you change the detection cycle frequency from the default 22 hours to 11 hours, the number of clients that the WSUS server can support is reduced to 7,500 clients.
If client computers do not report back to the WSUS server after you change the detection cycle frequency, you must delete all the current events from the tbEventInstance table. To do this, run the following command in SQL Query Analyzer:
TRUNCATE TABLE dbo.tbEventInstance
Additionally, you can stop the automatic deletion process and then increase the frequency of the deletion process. After you increase the frequency of the deletion process, WSUS deletes rows in smaller chunks, but maintains the size of the tbEventInstance table.
To stop the automatic deletion process and to set the frequency of the deletion process to 1 hour, run the following command in SQL Query Analyzer:
UPDATE dbo.tbConfigurationB SET AutoPurgeDetectionPeriod = 1
This command runs the deletion process every hour. After you run this command, WSUS deletes 24,000 events per day at the rate of 1,000 events per hour. This is the highest frequency that can be set for the deletion process.
To calculate the correct automatic deletion frequency and the correct detection cycle frequency, you must know the number of WSUS clients.
Use the following formulas to calculate the minimum frequency for the deletion process and the detection cycle frequency:
Minimum deletion process frequency: (24/DF) x CL
Detection cycle frequency: (CL/PF) x 24
Note DF is the detection cycle frequency, CL is the number of WSUS clients, and PF is the minimum purge frequency.
For example, if there are 4,000 WSUS clients and if you set the detection cycle frequency to 8 cycles per day, approximately 32,000 events can be logged to the tbEventInstance table. The maximum number of events that can be removed by the deletion process per day is 24,000 events when you set the deletion frequency to 1 hour. Therefore, you can reduce the detection cycle frequency so that the number of events that are generated by the clients is less than 24,000.