J2SE 1.4.0 for the Solaris Operating Environment, SPARC Platform Edition, supports 64-bit operation on 64-bit Sparc-v9 platforms when using the Java HotSpotTM Server VM. This allows support for heaps greater than 4 Gbytes, which is the absolute maximum that can be supported by a 32-bit VM. The Java HotSpot Server VM includes support for either 32-bit or 64-bit operation by using an appropriate command-line flag. When using the 64-bit VM a performance penalty of approximately 15% to 25% may be observed, depending on the amount of time your program spends accessing reference variables. J2SE 1.4.0 does not support 32-bit shared libraries, when running the 64-bit VM. Native (Java Native Interface) code must be recompiled in 64-bit mode.