Streaming Replication: sql error on standby

Hi,

Sql query "select pg_last_xlog_receive_location(); " does not work during startup of standby database.
TestScenario;
We have a active-standby system with PostgreSQL Streaming Replication beta2. If the active database is up the database is in use (read/write queries will be performed). Then the standby PostgreSQL SR will be started (the complete database from the active side is copied to the standby side; nec. Files for starting streaming replication are created). Directly after the possibility to connect to the standby system, the above given sql query will be executed. To this timepoint the sql query delivers an error. To a later timepoint (all wal segments are completly incooperated) the query delivers a valid result.
Question:
What is the reason for the error?
Exists a command to find out if the standby database is really active to accept/can work with sql commands?

BR
Ingo

Best Regards/mfG
Ingo Sander
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