WAL compatibility between Primary and Standby Server, chained clients

Hello!

I have questions about the streaming replication and about the WALs on the primary vs. standby servers.

How does the standby server decides when to write/rotate WAL files? Is this in sync how the primary server does this (ie. in the streaming replication protocol there are also signal when to rotate the WAL files)? Or does the standby server act totally on its own and decides itself when to rotate WAL files?

In the first case, are the WAL files between primary and standby server identical (so for example I could use a WAL file from a standby server with the base backup from a primary server)?

These questions came into my mind as we are doing a backup of the standby server using barman. Our standby server fell out of sync and had to resynced from the primary. Should a chained-downstream replication client (ie barman) automatically resync with the standby or is it necessary to re-initialize the replication from the standby to downstream clients?

Thanks
Klaus

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Klaus Darilion, Head of Operations

nic.at GmbH, Jakob-Haringer-Straße 8/V

5020 Salzburg, Austria