IBM Support

Why are IBM i ACS 5250 functions not working after updating to Java 26?

Question & Answer


Question

Why are IBM i Access Client Solutions (IBM i ACS) 5250 functions like launching a session or opening Session Manager failing?

Launching a 5250 session can generate a message "Invalid Session Profile.  No sessions could be started because this is not a valid session profile".  Also, the Session Manager or a 5250 session may open a very small window that only shows the window control icons and if expanded the window will be blank.

Cause

This is caused by running IBM i ACS with a distribution of Java 26.  Java 26 makes changes that the IBM i ACS 5250 emulator is incompatible with.

Answer

Java 26 is a Short-Term Support (STS) release of Java and therefore should not be used in a production environment with enterprise software.

Only Long-Term Support (LTS) releases of Java should be used with IBM i ACS.  The current LTS releases of Java are Java 8; Java 11; Java 17; Java 21 & Java 25.

Removing Java 26 and replacing it with a LTS release of Java will resolve the issue.

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Document Information

Modified date:
20 May 2026

UID

ibm17273000

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