SAP Basis Tech Supports

Symptom

After you update your SAP MaxDB instance to Version 7.7 or higher, the system performance is poor.
Problem identification:
a) You notice a high CPU usage (using operating system tools such as “sar”, “top” or “glance”). In particular, the CPU system part is high.
b) When you call more detailed information about the SAP MaxDB kernel process (for example, using “glance”), you notice that a very high number of “sched_yield” system calls per second are performed.
c) When you issue SAP MaxDB console commands (x_cons show active) to the database instance, you notice that a large number of user tasks have the status “*IO Wait (R)” or “**IO Wait (R)”
(’*’ directly before the status means that the task is in the run queue).
Other terms

1173347, sched_yield, 7.7, I/O, IO, system, CPU, central processing unit, run queue
Reason and Prerequisites

Prerequisites:
a) You use SAP MaxDB Version 7.7 or higher.
b) Operating system: Up to now, the symptom has been noticed only on HP-UX 11.23 (However, the problem may also occur on other platforms).
Solution

Workaround:
If no MaxDB version is available in which this problem is solved, you can improve the performance as follows:
Reduce the number of I/O workers (parameter MaxIOPoolWorkers), for example, to the volume number (however, the minimum number is 10).
To activate this parameter change, you must restart the database instance.
After you implement a MaxDB version in which this error is corrected, you must reset the value of the parameter MaxIOPoolWorkers to the default value (= 0).
Solution:
The problem is corrected in the following SAP MaxDB versions:
7.7.04 Build 33 (PTS 1173353)
7.7.06 Build 11 (PTS 1173356)
7.7.07 Build 05 (PTS 1173357)
7.8.00 Build 14 (PTS 1173348)
7.8.01 Build 00 (PTS 1173348)