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It is now possible for 64-bit builds to allocate amounts of memory limited only by the OS. It may be wise to use OS facilities (e.g. ‘ulimit’ in a ‘bash’ shell, ‘limit’ in ‘csh’), to set limits on overall memory consumption of an R process, particularly in a multi-user environment. A number of packages, particularly those using Java, need at least 4GB of virtual memory.