IBM Support

z/OS Connect CPU usage increases after upgrading Java

Troubleshooting


Problem

After you upgrade to Java™ 8.0.6.25 from Java V8.0.6.15, the amount of CPU that z/OS Connect uses goes up unexpectedly high. The new level of Java introduces a change that seems to cause higher CPU utilization in the z/OS Connect server. You capture a number of MVS System dumps that show the processing is in JITW.

Cause

SSL Session IDs are not being reused when SSLEngine does not receive the proper SSL or TLS close notification message from the peer.

Diagnosing The Problem

IBM requested the following diagnostic data for analysis of the problem:
  • IBMUSSE2 diagnostic trace data (sent to standard out) that you can request by setting:
    -Djavax.net.debug=all
  • Copy of the Java.security file
  • Full output of the "java-version" command
  • z/OS Connect messages.log
  • SMF 70 and SMF 72 records

Resolving The Problem

If z/OS Connect is using a high amount of CPU after you upgrade Java:
  1. Upgrade to Java 8.0.6.36 (or higher), which includes APAR IJ34146 and provides a system property that allows you to specify whether the JSSE implementation throws an exception
  2. Set the following property in the jvm.options file for z/OS Connect so Java does not throw an SSLException if a close or notify is not received from the peer:
    -Dcom.ibm.jsse2.sslEngineCloseNotifyReceive=false

Document Location

Worldwide

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Product Synonym

z/OS Connect Enterprise Edition ZCEE z/OS Connect OpenAPI 2

Document Information

Modified date:
14 February 2023

UID

ibm16602763