Saturday, October 1, 2016

Java updates - CPU and PSU

     A colleague recently asked which of these Oracle Java updates he should install onto his new computer.

     The answer to that question requires understanding the difference between a CPU and a PSU.  According to Oracle: 
CPU - Java SE Critical Patch Updates contain fixes to security vulnerabilities and critical bug fixes. Oracle strongly recommends that all Java SE users upgrade to the latest CPU releases as they are made available. 
PSU - Java SE Patch Set Updates contain all of fixes in the corresponding CPU, as well as additional non-critical fixes. Java PSU releases should only be used if you are being impacted by one of the additional bugs fixed in that version. The release notes call out the additional fixes available in Java SE PSU releases.
[link].  Further, the subsequent CPU release will contain all of the additional bug fixes from the current PSU.

     Finally, both CPUs and PSUs are cumulative, so you only have to install the latest version to receive all of the current and previous updates.  However, PSUs may contain a different patching mechanism.  [link to PDF at p.25]  Thus, once a PSU has been installed, you would need to continue  using PSUs.

     Thus, unless you are being impacted by some of the additional bugs that were fixed in the PSU, you should use the CPU.

- Henry Park

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