The quota of background copy (configured on the intercluster link) is divided evenly between  all nodes that are performing background copy for one of the eligible relationships. This  allocation is made irrespective of the number of disks for which the node is responsible. Each  node in turn divides its allocation evenly between the multiple relationships that are  performing a background copy. The default value of the background copy is 25MBps per volume. Important:  The background copy value is a system-wide parameter that can be changed  dynamically, but only on a per-system basis and not on a per-relationship basis. Therefore,  the copy rate of all relationships changes when this value is increased or decreased. In  systems with many remote copy relationships, increasing this value might affect overall  system or intercluster link performance. The background copy rate can be changed to  1 - 1000 MBps. MM/GM relationships preserve the space-efficiency of the master. Conceptually, the  background copy process detects a deallocated region of the master and sends a special  zero buffer  to the auxiliary. If the auxiliary volume is thin-provisioned and the region is deallocated, the special buffer  prevents a write and, therefore, an allocation. If the auxiliary volume is not thin-provisioned or  the region in question is an allocated region of a thin-provisioned volume, a buffer of “real”  zeros is synthesized on the auxiliary and written as normal. This section describes two methods that can be used to establish a synchronized  relationship. The full synchronization after creation method is the default method. It is the simplest method  in that it requires no administrative activity apart from issuing the necessary commands.  However, in certain environments, the available bandwidth can make this method unsuitable.  Use the following command sequence for a single relationship: In this method, the administrator must ensure that the master and auxiliary volumes contain  identical data before creating the relationship by using the following technique: With this technique, do not allow I/O on the master or auxiliary before the relationship is  established. Then, the administrator must run the following commands: GLYPH<SM590000> Run  startrcrelationship  without the  -clean  flag. GLYPH<SM590000> Run  mkrcrelationship  with the  -sync  flag. GLYPH<SM590000> A complete tape image (or other method of moving data) is copied from one disk to the  other disk. GLYPH<SM590000> Both disks are created with the security delete feature to make all data zero. GLYPH<SM590000> Run  mkrcrelationship  without specifying the  -sync option. GLYPH<SM590000> Run  startrcrelationship  without specifying the  -clean  option. 11.6.16 Thin-provisioned background copy 11.6.17 Methods of synchronization Full synchronization after creation Synchronized before creation Chapter 11. Advanced Copy Services  531