If your configuration depends on content databases -- for example, dynamic applications defined by the AppID service -- you need to download and install the corresponding database prior to enabling chassis cluster (i.e. before step # 3 described in the KB).
If you don't have the databases downloaded, you won't be able to commit your saved configuration (error about undefined junos: dynamic applications, etc.). And once you enable chassis cluster, you won't be able to download and install the databases (errors about failing to push the package to the backup RE).
If you get to that point, you would have to once again disable chassis cluster, then enable AppID, download & install the database, then enable chassis cluster again, etc.
Reference: KB21134 (CEC Juniper Community
)
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NIKOLAY SEMOV
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