JDK-8155886 : Release Note: Various GC combinations have now been removed
  • Type: Sub-task
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 9
  • Priority: P4
  • Status: Closed
  • Resolution: Delivered
  • Submitted: 2016-05-03
  • Updated: 2017-09-22
  • Resolved: 2016-12-13
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The GC combinations that were deprecated in JDK 8 have now been removed. This means that the following GC combinations no longer exist: 
* DefNew + CMS 
* ParNew + SerialOld 
* Incremental CMS 
The "foreground" mode for CMS has also been removed. 

The command line flags that were removed are: `-Xincgc, -XX:+CMSIncrementalMode, -XX:+UseCMSCompactAtFullCollection, -XX:+CMSFullGCsBeforeCompaction` and `-XX:+UseCMSCollectionPassing`. 

The command line flag `-XX:+UseParNewGC` no longer has any effect. ParNew can only be used with CMS and CMS requires ParNew. Thus, the `-XX:+UseParNewGC` flag has been deprecated and will likely be removed in a future release.