IBM User Guide for Java V7 on Windows > Product overview > What's new

What's New: IBM J9 V2.6 JVM


SR4

  1. Support for dynamic machine configuration changes

    A new command-line option, -Xtune:elastic, is available to turn on JVM function at run time that accommodates dynamic machine configuration

  2. Change to default behavior for -Xcompressedrefs

    The -Xcompressedrefs is now enabled by default when the value of the -Xmx option is less than or equal to 25 GB, for all 64-bit operating systems other than z/OS. Use the -Xnocompressedrefs option to revert to the previous behavior. For z/OS operating systems, or values of -Xmx that are greater than 25 GB, compressed references are still disabled by default.

  3. Enable caching of LUDCL

    A new system property is available, -Dcom.ibm.enableClassCaching, to enable caching of the Latest User Defined Class Loader (LUDCL). By reducing repeated lookups, Java applications that use deserialization extensively can see a performance improvement.

  4. Use of java.util.* package and classes

    The SDK now uses the Oracle implementation of the java.util.* package, including all classes within the package. Earlier releases of the SDK used customized versions of the Apache Harmony class libraries. This change establishes a common implementation point for the java.util.* package, enabling consistent performance and behavior characteristics across Java implementations. Existing applications are expected to function without problems. However, if testing exposes any issues, contact your IBM service representative.


SR3

  1. IBM GBK converter

    By default the IBM GBK converter follows Unicode 3.0 standards. A new system property value for -Dfile.encoding is available to force the IBM GBK converter to follow Unicode 2.0 standards.


SR2

  1. Improved hashing algorithms

    An improved hashing algorithm is available for string keys stored in hashed data structures. You can adjust the threshold that invokes the algorithm with the system property, jdk.map.althashing.threshold. This algorithm can change the iteration order of items returned from hashed maps.

    An enhanced hashing algorithm is used for...

      javax.xml.namespace.QName.hashCode()

    This algorithm can change the iteration order of items returned from hashed maps. You can control the use of this algorithm with the system property...


SR1

  1. Changes to locale translation files

    Changes are made to the locale translation files to make them consistent with Oracle JDK 7. The same changes were also applied to the IBM SDK for Java V6 for consistency with Oracle JDK 6.

  2. JVM optimizations

    The IBM J9 V2.6 virtual machine includes new optimizations for Java monitors that are expected to improve CPU efficiency. New locking optimizations are also implemented that are expected to reduce memory usage and improve performance.

  3. Java Attach API

    Connections to virtual machines through the Java Attach API have a new default state. By default, the Attach API is enabled on ALL platforms. The exception is that for security reasons, processes on z/OS using the default z/OS OMVS segment cannot enable the Attach API.


    Parent: What's new








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