Reeving an error while taking the backup using "pg_basebackup" utility.

Hi All,

We are using below command to take the backup of the database.

*$PGHOME/bin/pg_basebackup -p 5433 -U postgres -P -v -x --format=tar --gzip
--compress=1 --pgdata=- -D /opt/rao *

While taking the backup we have received below error.

transaction log start point: 285/8F000080

pg_basebackup: could not get transaction log end position from server:
FATAL: requested WAL segment 00000001000002850000008F has already been
removed

Please guide me why and how to handle this error. Do you want me to change
any of the option in my pg_basebackup command let me know.

Please clarify me what it means *--pgdata=--D* in my above * pg_basebackup *
command.
--
Regards,
Raghavendra Rao J S V