Does java garbage collection log entry "Full GC (System)" mean some class called System.gc()?

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What does "Full GC (System)" entry in the garbage collection logs mean? That some class called System.gc() ?

My garbage collection logs has two different entry types for 'full gc'? One with the word 'System', the other without. What's the difference?

(Update: I searched on this term and didn't find a definitive answer, only a few questions. So I thought I'd post it).

System:

164638.058: [Full GC (System) [PSYoungGen: 22789K->0K(992448K)] [PSOldGen: 1645508K->1666990K(2097152K)] 1668298K->1666990K(3089600K) [PSPermGen: 164914K->164914K(166720K)], 5.7499132 secs] [Times: user=5.69 sys=0.06, real=5.75 secs]

No-System:

166687.013: [Full GC [PSYoungGen: 126501K->0K(922048K)] [PSOldGen: 2063794K->1598637K(2097152K)] 2190295K->1598637K(3019200K) [PSPermGen: 165840K->164249K(166016K)], 6.8204928 secs] [Times: user=6.80 sys=0.02, real=6.81 secs]

GC Options

Our gc-related java memory options are: -Xloggc:../server/pe/log/jvm_gc.log -XX:+PrintGCTimeStamps -XX:+PrintGCDetails

We do not '-XX:+DisableExplicitGC', so it's possible some errant class does call System.gc()

fwiw, our full jvm options:

-Xms3072m -Xmx3072m -XX:+HeapDumpOnOutOfMemoryError -XX:-UseGCOverheadLimit -Xloggc:../server/pe/log/jvm_gc.log -XX:+PrintGCTimeStamps -XX:+PrintGCDetails -XX:MaxPermSize=256m -XX:+UseCompressedOops

thanks in advance,

will

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