DB2 Connect User's Guide

Performance Troubleshooting

If DB2 Connect users are experiencing long response times during large queries from hsot or AS/400 servers, the following areas should be examined for the possible cause of the performance problem:

1. For queries which result in returning large data blocks from the host or AS/400 server (usually 32K of data and above), ensure that the database manager configuration parameter RQRIOBLK is set to 32767. This can be done using the Command Line Processor (CLP) as follows:

      db2 update database manager configuration using RQRIOBLK 32767
   

2. If VTAM is used in the connection to the host or AS/400 server, look under "switched major node" configuration for the value of the PACING parameter. On the DB2 Connect workstation, examine the communication setup of the "LU 6.2 Mode Profile" for IBMRDB mode definition. In this definition, ensure the value for the "Receive pacing window" parameter is less than or equal to the PACING value defined on VTAM. A common value for "Receive pacing window" on the DB2 Connect workstation and "PACING" on VTAM is 8.

3. Ensure the maximum RU size defined in the IBMRDB mode definition is set to a suitable value. We recommend not less than 4K for connections using Token-ring hardware. For connections using Ethernet hardware, note the maximum Ethernet frame size of 1536 bytes, which may be a limiting factor.

4. Consult with the VTAM administrator in your environment to ensure that VTAM is using "adaptive pacing" in LU-LU sessions with your DB2 Connect workstation.

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