This week, I was teaching an 11g Data Guard course in Duesseldorf – my home location. One question that arose in that course was, whether it is possible to run a Logical Standby Database not beeing in archive mode.
Brief explanation: Unlike Physical Standby Databases, the Logical Standby is a quite independent Database that tries to do the same SQL Statements that arose at the Primary to keep up to date with it. In order to be able to do so, it gets the redo protocol transmitted from the primary and analyzes it (with Logminer technique). That redo protocol is stored in Archive Logs on the Logical Standby, which can’t be turned off, of course.
But also, when the SQL Apply on the standby changes blocks, it writes its own redo protocol into its own Online Logfiles and (by default) archives them. Sometimes, this is not needed, because customers use their Logical Standby as kind of “cheap replication” and do not use it for HA purpose. So can we turn off Archive Logging on the Logical Standby? I saw that in place already at a (not reference, unfortunately) customer site, so the short answer was: Yes, we can🙂
I tested it then myself and it really works. We can turn off archivelogging on the Logical Standby even with usage of the Data Guard Broker and with no warnings from it. But it seems, as if that is only possible with archiver transmission from the Primary to the Logical Standby. Otherwise (with LogXptMode async or sync), the transmission to the Logical Standby stops.