Replication Server 15.5 supports 64-bit computing platforms, which provide Replication Server with a large amount of virtual memory space and removes the maximum memory constraint of 2GB.
In addition, all the available Replication Server counters are now defined as 64-bit, which allows high-precision computations in Replication Server.
See Chapter 3, “Upgrading or Downgrading Replication Server” in the Replication Server Configuration Guide to migrate to 64-bit platforms and Chapter 4, “Performance Tuning” in the Replication Server Administration Guide Volume 2 to configure support for 64-bit platforms.