Hi @guimx,
Thank you for the report. Diagnostics indicate that the ARC instance associated with your account is receiving extreme memory pressure warnings from the phone’s operating system. iOS very likely can’t run ARC with this large of a database.
In order for ARC to successfully play library content with poor or limited connectivity, Roon needs to synchronize information about your music library onto your mobile device. This database sync is a separate process from downloading tracks for offline playback - ARC needs to retain a list of all “objects” in your library to prevent database corruption and maintain parity with your Roon database. While the data synchronized is much more compact than what is stored in the RoonServer, 700,000 tracks is very likely still too big for a mobile device. Aside from limitations in device performance, there are also restrictions on resource usage imposed by Apple and Google which make this scale of data transfer, synchronization, and storage impractical within a mobile app.
The current estimation for maximum compatible library size varies widely by the makeup of your library (file format, etc). The team estimates the upper range to be between 100k-200k tracks, depending on the processing power of the phone.
If offline mobile playback with ARC is a priority, we generally recommend 1) creating a Backup of your current database for due diligence and 2) creating a fresh Roon database with only a portion of your library imported via Watched Folders (start at 100k tracks). This will lower the object count sufficiently for ARC to sync and then maintain the database without resource constraints and memory pressure.
Hopefully, this is helpful. Thank you!