Tuning Full GC Events In The OACORE JDK 6 Java Virtual Machine (Doc ID 851765.1)

Last updated on AUGUST 08, 2016

Applies to:

Oracle Applications Technology Stack - Version 12.0.5 to 12.1.3 [Release 12.0 to 12.1]
Information in this document applies to any platform.

Goal

If you are experiencing continual full GC cycles and are running the following configuration, this document may be useful

Important: This document is relevant for Sun JDK 6 (OS's: Linux and Sun only!)
Release 12 or 12.1.1 EBusiness Suite

Note: This document is not suitable for IBM AIX operating systems!


After analyzing your GC logs you may notice continuous long GC pauses similar to the following.

 

OC4J~oacore~default_group~<n>.log

898753.288: [Full GC 825983K->743065K(913024K), 15.8442715 secs]
898772.243: [Full GC 825983K->750548K(913024K), 13.3512933 secs]
898798.124: [Full GC 825983K->731902K(913024K), 13.3466676 secs]
898832.082: [Full GC 825983K->738500K(913024K), 13.1591655 secs]
898857.239: [Full GC 825973K->728250K(913024K), 16.4536985 secs]
898883.409: [Full GC 825983K->738357K(913024K), 12.9196927 secs]
898900.955: [Full GC 825973K->752265K(913024K), 13.2905248 secs]
898916.459: [Full GC 825983K->752385K(913024K), 13.3318852 secs]
898944.577: [Full GC 825983K->737827K(913024K), 15.8495953 secs]
898965.636: [Full GC 825983K->747989K(913024K), 13.2199067 secs]
899036.290: [Full GC 825983K->754679K(913024K), 13.3357689 secs]

These pauses will result in performance issues to the end user. Occasional large full GC sweeps are ok, but continual long full GC as above are not healthy.

Here is what relatively healthy GC activity looks like:

902130.499: [GC 829181K->716211K(935296K), 0.2895464 secs]
902220.498: [GC 833715K->721542K(935296K), 0.3210096 secs]
902400.049: [GC 839046K->725265K(936768K), 0.3448279 secs]
902400.394: [Full GC 725265K->652064K(936768K), 8.5214844 secs]
902455.778: [GC 771040K->661918K(935296K), 0.1618026 secs]
902471.215: [GC 780894K->671024K(940928K), 0.2324366 secs]
902562.728: [GC 796452K->680040K(937600K), 0.2932150 secs]
902641.471: [GC 805480K->683929K(951680K), 0.3314957 secs]

Solution

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