Filesystem asynch replication issue: Destination pool full

Hello,

I have a customer with two Unity 400 systems. Both are configured for file and block access. Filesystems and block luns reside on the same storage pool. Each Unity has one hybrid storage pool. File systems are asynchronous replicated between Unity systems. Replication interval is 10 min. Source Filesystems on Unity are configured with snapshots. Unity code is 4.4.1.

Sometimes the following replication Warning occurs:

Alert Text: Replication session rep_sess_res_9_res_14_CKM00123456789_CKM00987654321 can not update destination because destination pool is full.

About one minute later a notice is displayed that replication is working again properly.

File systems are smaller than 8TB with about 75% free space in each filesystem.

Storage Pools on Unity (both source and target) have more than 50TB free space in pool.

What is wrong here?

Robert