Hello,
solved.
This is not a postgres issue.
The system was used in HA-cluster with streaming replications.
The hidden files I asked for were created probably by broken (killed)
rsync. It uses such file-format for temporary files used during copying.
This rsync is used by master to slave database synchronization (full
on-line backup of master database to slave node) before starting postgres
in hot-standby mode on slave the node...
Best Regards, Andrej