The deprecated exclusive mode promises to make a difficult problem simple but doesn't live up to that promise. That's why it was replaced externally in 9.6 and why pg_basebackup has not used exclusive backups since it was introduced in 9.2.
Non-exclusive backups have been available since 9.6 and several third-party solutions support this mode, in addition to pg_basebackup.
The recently introduced recovery changes will break current automated solutions so this seems like a good opportunity to make improvements on the backup side as well.
I'll submit a patch for the 2019-01 commitfest.
-1 for removal, in this release
It's not there because anyone likes it, it's there because removing it is a risk
Recent changes are the reason to keep it, not a reason to remove.
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Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services