IBM Tivoli Composite Application Manager for Application Diagnostics, Version 7.1.0.1

Garbage Collection Cycle attributes

The Garbage Collection Cycle attribute group provides information about a single garbage-collection cycle that the Java Virtual Machine hosting the application server performed.

The Garbage Collection Cycle attributes report the free heap space both before and after garbage collection, the heap space freed, and the number of objects moved during garbage collection. Use the Garbage Collection Cycle attributes in situations to examine the results of a particular garbage collection.

The attributes within this group are used to build the Garbage Collections - Selected Allocation Failure workspace.

Allocation Failure Number

The identifier assigned to the allocation-failure block for which the JVM ran the current garbage-collection cycle, which is associated with a bar in the Heap Usage - History bar chart. If your Java code called System.gc to invoke garbage collection, this number is 0. Format is positive integer.

ASID

The identifier (decimal) assigned to the address space running this servant region.

Compact (ms)

The time (in milliseconds) required for the compaction phase of the garbage-collection cycle. Format is positive integer.

Compaction Reason

The code describing the reason garbage collection was initiated. Format is positive integer. The compaction codes are:


Reasons for initiating garbage collection

Compaction Code Definition
1 Insufficient free space for the allocation request following the mark and sweep phases.
2 The heap is fragmented and will benefit from a compaction.
3 Less than 15% free space available.
4 A call to System.gc requested garbage collection.
5 Less than 5% free space available.
6 Less than 128K free space available.
7 Parameter Xcompactgc specified.
8 The transient heap has less than 5% free space available.
9 The heap is fragmented (this code marks additional reasons for compaction apart from compaction code 2).

Final References

The number of final reference objects collected during this garbage-collection cycle. Format is positive integer.

Garbage Collection Date and Time

The date and time the Java Virtual Machine invoked the garbage collector. The valid format is a 16-character timestamp. This attribute was designed for logging and reporting data-collection times rather than for creating situations. To specify a time and date for comparison and testing, use attributes from the Universal Time or Local Time groups.

Note to Solaris and HP-UX users: Since allocation-failure information is not recorded on these platforms, this column is always empty on these platforms.

Garbage Collection Number

The number of this garbage-collection cycle. Format is positive integer.

Heap Capacity (Kbytes)

The total number of kilobytes allocated to the main heap after this garbage-collection cycle. Format is positive integer.

Heap Free (%) after GC

The percentage of heap space that is available after this garbage-collection cycle. Format is decimal (formatted to 1 decimal place).

Heap Space Free (Kbytes)

The number of kilobytes available within the heap after this garbage-collection cycle. Format is positive integer.

Interval (sec)

The length (in seconds) of the sampling interval. Format is positive integer.

KBytes Free at Start of GC

The number of kilobytes available in the heap before garbage collection began. Format is positive integer.

Kbytes Freed

The number of kilobytes freed by the garbage collector. Format is positive integer.

Kbytes Moved

The number of kilobytes moved on the heap during this compaction. Format is positive integer.

Kbytes Used

The number of kilobytes in the heap that were in use after this garbage-collection cycle. Format is positive integer.

Mark (ms)

The time (in milliseconds) required for the mark phase of the garbage-collection cycle. Format is positive integer.

Node Name

The name of the system on which the server is running. Alphanumeric string.

Objects Moved

The number of objects the garbage collector moved during this compaction. Format is positive integer.

Origin Node

The name of the server subnode. Alphanumeric string. Maximum 128 characters.

Phantom References

The number of phantom reference objects collected during this garbage-collection cycle. "Phantom" refers to a specific Java class that defines object reachability. Format is positive integer.

Process ID

The unique identifier of the JVM process (the class ID of the JVM). Format is positive integer.

Sample Date and Time

The date and time the Tivoli Enterprise Management Agent collected the data. The valid format is a 12-character timestamp. For the STR and SCAN functions, the format is MM/DD/YY HH:MM:SS; the following table shows the values contained in this character string:


Format of the 12-character timestamp

Character String Meaning
MM Month
DD Day
YY Year
HH Hour
MM Minute
SS Second

Example: 09/13/06 18:32:03 indicates the data was collected on September 13, 2006, at 18:32:03.

This attribute was designed for logging and reporting data-collection times rather than for creating situations. To specify a time and date for comparison and testing, use attributes from the Universal Time or Local Time groups.

Server Name

The name of the WebSphere application server. Alphanumeric string.

Soft References

The number of soft reference objects collected during this garbage-collection cycle. "Soft" refers to a specific Java class that defines object reachability. Format is positive integer.

Sweep (ms)

The time (in milliseconds) required for the sweep phase of the garbage-collection cycle. Format is positive integer.

Time to Complete (ms)

The time (in milliseconds) required to complete this garbage-collection cycle. Format is positive integer.

Weak References

The number of weak reference objects collected during this garbage-collection cycle. "Weak" refers to a specific Java class that defines object reachability. Format is positive integer.

Additional information:


Parent topic:

Attributes for ITCAM Agent for WebSphere Applications