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-Xmint / -Xmaxt

Sets the minimum and maximum proportion of time to spend in the garbage collection (GC) process as a percentage of the overall running time that included the last three GC runs.

  • If the percentage of time drops to less than the minimum, the OpenJ9 VM tries to shrink the heap.
  • If the percentage of time exceeds the maximum, the VM tries to expand the heap.


  • This option applies only to GC policies that include stop-the-world (STW) operations, such as -Xgcpolicy:optthruput.


Setting Effect Default
-Xmint<value> Set minimum time in GC 0.05
-Xmaxt<value> Set maximum time in GC 0.13

For the gencon GC policy, the values apply only to the tenure part of the heap. For the balanced, optthruput, and optavgpause GC policies, these values apply to the whole heap. This option cannot be used with the metronome GC policy (-Xgcpolicy:metronome) because the heap is always fully expanded.

See also