To choose the segment allocation, use the alter connection or alter route command with the set disk_affinity option. The syntax is:
alter connection to dataserver.database set disk_affinity to [ 'partition' | 'off' ]
alter route to replication_server set disk_affinity to [ 'partition' | 'off' ]
partition is the logical name of the partition to which you want to allocate the next segment for the connection or route.
Each allocation directive is called a “hint” because Replication Server can override the allocation if, for example, the allocated partition is full or has been dropped. If Replication Server overrides the hint, it allocates segments according to the default mechanism described in Figure 4-12.
Replication Server checks for an allocation hint each time it allocates a new segment for a queue. Each hint is stored in the rs_diskaffinity system table. Each partition may have many hints, but each stable queue can have only one hint.
Successfully using disk allocation to improve performance depends on the architecture and other characteristics of your site. One way to improve overall throughput is to associate faster devices with those stable queues that process more slowly.
In addition, if new partitions are added after all connections are in place, the new partitions are not used until the existing ones are filled. You can force a connection to use the new partition by adding allocation hints.
