Tuning Enterprise Extender-specific buffer pools

Enterprise Extender performance degradation can be caused by poorly tuned buffers. Monitor and tune the T1BUF and T2BUF buffer pools to minimize the number of expansions. Minimizing buffer pool expansions decreases internal buffer overhead processing, which should increase throughput while reducing CPU consumption. Also, the T1BUF and T2BUF pools are used instead of the TIBUF buffer pool. Increasing the buffer pool values for the T1BUF, T2BUF, or both might decrease the buffers necessary for the TIBUF pool. You should also monitor and tune the TIBUF pool.

Use IBM® Health Checker for z/OS® to check whether the T1BUF and T2BUF start option definitions for the initial number of buffers in the pool are greater than the default value when Enterprise Extender (EE) is not being used. You can also use Health Checker to check whether the initial number of buffers specified for these two buffer pools is equal to the default value when EE is being used with QDIO or HiperSockets™. For more details about IBM Health Checker for z/OS, see z/OS Communications Server: IP Diagnosis Guide.

The following is a buffer pool display example.

d net,bfruse,buf=(ti,t1,t2)                                               
IST097I DISPLAY ACCEPTED                                               
IST350I DISPLAY TYPE = BUFFER POOL DATA
IST920I TI00     BUFF SIZE  800         EXP INCREMENT   60           
IST921I          TIMES EXP  0           EXP/CONT THRESH 120   / *NA* 
IST922I          CURR TOTAL 360         CURR AVAILABLE  85          
IST923I          MAX TOTAL  360         MAX USED        302  
IST924I -------------------------------------------------------------                                         
IST920I T100     BUFF SIZE  1340        EXP INCREMENT   36            
IST921I          TIMES EXP  3           EXP/CONT THRESH 15    / 111    
IST922I          CURR TOTAL 112         CURR AVAILABLE  112            
IST923I          MAX TOTAL  112         MAX USED        69             
IST924I -------------------------------------------------------------  
IST920I T200     BUFF SIZE  2028        EXP INCREMENT   32             
IST921I          TIMES EXP 406920       EXP/CONT THRESH 7     / 103    
IST922I          CURR TOTAL 104         CURR AVAILABLE  104            
IST923I          MAX TOTAL  1608        MAX USED        1576           
IST314I END

In this example, the T2BUF (T200) buffer pool expanded 406,920 times. At any given time, the maximum number of T2BUF buffers used at one time was 1576. This example indicates that the T2BUF buffer pool is thrashing, constantly expanding and contracting to meet the needs of its environment. A large number of expansions indicates that buffer pool tuning is warranted. In this case, coding a base allocation of 1576 buffers or more will eliminate the buffer pool thrashing for the T2BUF buffer pool. Use a similar approach when tuning your T1BUF buffers. In this example, the T1BUF pool does not need tuning (three expansions is considered minor).