IBM User Guide for Java V7 on Windows > Reference > Command-line options > Garbage Collector command-line options

-Xgcpolicy

Controls the behavior of the Garbage Collector.

-Xgcpolicy:< balanced | gencon | optavgpause | optthruput >

gencon

The gencon policy (default) uses a concurrent mark phase combined with generational garbage collection to help minimize the time that is spent in any garbage collection pause. This policy is particularly useful for applications with many short-lived objects, such as transactional applications. Pause times can be significantly shorter than with the optthruput policy, while still producing good throughput. Heap fragmentation is also reduced.

balanced

The balanced policy uses mark, sweep, compact and generational style garbage collection. The concurrent mark phase is disabled; concurrent garbage collection technology is used, but not in the way that concurrent mark is implemented for other policies. The balanced policy uses a region-based layout for the Java™ heap. These regions are individually managed to reduce the maximum pause time on large heaps and increase the efficiency of garbage collection. The policy tries to avoid global collections by matching object allocation and survival rates. If you have problems with application pause times that are caused by global garbage collections, particularly compactions, this policy might improve application performance. If you are using large systems that have Non-Uniform Memory Architecture (NUMA) characteristics (x86 and POWER platforms only), the balanced policy might further improve application throughput. For more information about this policy, including when to use it, see Balanced Garbage Collection policy.

optavgpause

The optavgpause policy uses concurrent mark and concurrent sweep phases. Pause times are shorter than with optthruput, but application throughput is reduced because some garbage collection work is taking place while the application is running. Consider using this policy if you have a large heap size (available on 64-bit platforms), because this policy limits the effect of increasing heap size on the length of the garbage collection pause. However, if your application uses many short-lived objects, the gencon policy might produce better performance.

optthruput

The optthruput policy disables the concurrent mark phase. The application stops during global garbage collection, so long pauses can occur. This configuration is typically used for large-heap applications when high application throughput, rather than short garbage collection pauses, is the main performance goal. If your application cannot tolerate long garbage collection pauses, consider using another policy, such as gencon.

Parent: Garbage Collector command-line options

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