Table 6-1 Supported -Xverbosegcoptions for Java 1.5.0.04 (continued)

filename writes output to the specified file.

[n][h][d][u][t]

n prevents appending the pid to the log filename.

 

h appends the hostname to the log file name.

 

u appends the username to the log file name.

 

d appends the date to the log file name.

 

t appends the time to the log file name.

At every selected garbage collection, the following 20 fields are printed. These values hold true for Java 1.5.0.04. Other versions may differ. To see the complete list of available fields for the Java version you are running, use

java ... -Xverbosegc:helpTable 6-2 Fields Captured in GC Log Data When Using -Xverbosegcprint options

%1 Type of garbage collection.

1 = scavenge (of new generation only)

2 = old generation GC or full GC

3 = complete background, concurrent mark and sweep (CMS) GC 4 = incomplete background, concurrent mark and sweep GC

11 = Ongoing CMS GC

%2 This value varies depending on the value of %1.

•When %1 is equal to 1, %2 indicates whether or not a parallel scavenge occurred. Possible values are:

—0: non-parallel scavenge

—n(>0): parallel scavenge with n number of parallel GC threads

•When %1 is equal to 2, %2 indicates that an old generation GC or full GC has occurred. Reasons for the GC are given as:

—1: Allocation failure, followed by a failed scavenge, leading to a full GC

—2: Call to System.gc made

—3: Tenured generation is full

—4: Permanent generation is full

—5: Scavenge followed by a train collection

—6: Concurrent-Mark-Sweep (CMS) generation is full

—7: Old generation expanded on last scavenge

—8: Old generation too full to scavenge

—9: FullGCAlot

—10: Allocation profiler triggered

—11: JVMTI-forced garbage collection

—12: Adaptive size policy

—13: Last ditch collection

—14: GC Locker-Initiated GC

—15: Heap Dump Triggered GC (HP implementation)

—16: Heap Dump Triggered GC

•When %1 is equal to 3, %2 indicates that a complete background, concurrent mark and sweep GC has occurred. Reasons for the GC are given as:

—1: Occupancy > initiating occupancy

—2: Expanded recently

—3: Incremental collection will fail

—4: Linear allocation will fail

—5: Anticipated promotion

•When %1 is equal to 4, %2 indicates that an incomplete background, concurrent mark and sweep GC has occurred as a result of exiting after yielding to foreground GC. The form for this data set is given as n.m where n is the GC reason as follows:

—1: Occupancy > initiating occupancy

—2: Expanded recently

Obtaining Garbage Collection Data

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