Replication Server 15.1 and later preallocates segments in the background to reduce segment allocation latency. Segment allocation imposes significant latency to writer threads especially when the RSSD is on a remote Adaptive Server.
When a writer thread needs a new segment, it checks whether the preallocated segment is available, if it is not, the thread requests to allocate the segment. Once the writer thread gets the new segment, a preallocation request is made so that the segment is allocated in the background. By the time the writer thread needs a new segment, it is already available.
Enable or disable segment preallocation using:
configure replication server set sqm_seg_prealloc to "on|off"
This command is static, which means you must restart the server for it to take effect. It supports only the server-level configuration.