Quote:
Originally Posted by victor50
I just added two books, converted them to EPUB and edited metadata, while on the other PC Calibre was open (and in server-mode). Database functions perfectly. The only thing is that it didn't refresh and there wasn't a possibility to force a refresh. After restart it did show the added books ok. Then, I think in the helpfile topic "CALIBRE_OVERRIDE_DATABASE_PATH" it says this is usefull when the external drive doesn't support locking, meaning that multiuser use is possible. Maybe @kovidgoyal could shed some more light on the matter
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FWIW I have been working with Kovid on calibre for more than 10 years, including in the database layer. I have some idea of what I am talking about.
Calibre loads the DB into memory when it starts. If you make changes it starts with the memory copy, changes it, then writes it to the DB. It does not check if the DB had been changed. If another calibre instance is running then the two memory copies are now out of sync. Changes in the other instance will overwrite those made by the first instance. For a certain class of changes the result will be a database that is not consistent with the rest of the library, sometimes to the point where there is significant data loss.
You can post all the "tests" you want. You can believe me or not. Neither changes the underlying fact that running multiple instances of calibre of the same library will eventually destroy your library.