Enhanced behavior for -Xdump:check on z/OS

[keithc-ca]

Issue or pull request number:
eclipse-openj9/openj9#23847

Overview:
The behavior of -Xdump:check has been enhanced on z/OS to validate dataset names specified in -Xdump:system options. This allows for earlier detection of improper JVM options improving the likelihood that an expected system dump will actually be produced instead of just a complaint that the dataset name is invalid.

Release target:
Eclipse OpenJ9 0.60.0

Applies to the following JDK versions:
E.g. 11 and later

Applies to the following platforms:
z/OS

[keithc-ca]

Some examples may clarify the new behavior.

When all dataset names are valid (as is the case with the defaults), no change is visible:

$ java -Xcheck:dump -version
java version "21.0.11-internal" 2026-04-21
IBM Semeru Runtime Certified Edition for z/OS (build 21.0.11-internal-adhoc.JENKINS.BuildJDK21s390xzosPersonal)
IBM J9 VM (build 21.0.11-internal-adhoc.JENKINS.BuildJDK21s390xzosPersonal-dsntest-5de00868719, JRE 21 z/OS s390x-64-Bit Compressed References 20260429_3867 (JIT enabled, AOT enabled)
OpenJ9   - 5de00868719
OMR      - 4a4463e1977
IBM      - 764a44bc845
JCL      - 166e9d03068 based on jdk-21.0.11+10)

When the -Xcheck:dump option is not used, the JVM behaves as before - the bad dataset name is reported if and when the dump is triggered (normal output is omitted here):

$ java -Xdump:system:events=user,dsn='BAD..NAME.X&DS' -version

When the -Xcheck:dump option is used, the JVM reports the problematic -Xdump options in the same format used by -Xdump:what and refuses to proceed:

$ java -Xdump:system:events=user,dsn='BAD..NAME.X&DS' -Xcheck:dump -version
JVMJ9VM268E The following -Xdump:system options contain invalid dsn specifications:
-Xdump:system:
    events=user,
    dsn=BAD..NAME.X&DS,
    range=1..0,
    priority=999,
    request=serial
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

If dump support is disabled, so is -Xcheck:dump. The JVM proceeds normally except for an additional message (normal output is again omitted here):

$ java -Xdump:none -Xcheck:dump -version
JVMJ9VM063W seekDumpAgent requires j9dmp29