I had used v2 for several years with no corruption issue.  Any number of ungraceful shutdowns and the DB never suffered.  But in the last few months since I switched to V3, it's happened three times already.  This version is definitely much more fragile.

Has anybody figured out how to use the supposed recovery tool?  I installed H2 and ran the command from the docs linked above, but it fails with 

Error: Could not find or load main class org.h2.tools.Recover
Caused by: java.lang.ClassNotFoundException: org.h2.tools.Recover

Wiping out and rebuilding the DB from scratch takes the better part of a week for me.  I'd really prefer not to have to do that every time the power goes out unexpectedly.

It finally completed scanning, and after manually restarting the server, it's now displaying the files.  My only comment so far is that there does not appear to be a "home" button.  The up button will only take you to the top of the category you're already in.  There seems to be no easy way to get back to the category selection page.  Possibly something you might want to add.

OK, I have tried updating to V3, and I'm not entirely sure it's working.  It has been scanning my directories for three straight days, and there is still "nothing in the database".  Is this normal?

I see no magazine or other categories to use.  Using the latest 2.1.5 version, the only categories available are comics, books, and raw files.

I just started using Ubooquity and it's still working its way through my collection.  Looking at the logs it appears that most (if not all) PDFs fail to be added.  Here's an example from the logs:

20191222 09:42:59 [Scanner thread] ERROR com.ubooquity.data.feeder.a - Failed to insert Z:\Vault\Books\Comics & Manga\Legend of Zelda\The Legend of Zelda - Majora's Mask & A Link to the Past [Eng TPB].pdf
java.lang.OutOfMemoryError: Java heap space
   at java.util.Arrays.copyOf(Unknown Source) ~[na:1.8.0_231]
   at java.io.ByteArrayOutputStream.grow(Unknown Source) ~[na:1.8.0_231]
   at java.io.ByteArrayOutputStream.ensureCapacity(Unknown Source) ~[na:1.8.0_231]
   at java.io.ByteArrayOutputStream.write(Unknown Source) ~[na:1.8.0_231]
   at org.apache.pdfbox.io.IOUtils.copy(IOUtils.java:68) ~[pdfbox-2.0.6.jar.6729965043262619269.tmp:2.0.6]
   at org.apache.pdfbox.io.IOUtils.toByteArray(IOUtils.java:50) ~[pdfbox-2.0.6.jar.6729965043262619269.tmp:2.0.6]
   at org.apache.pdfbox.pdmodel.encryption.SecurityHandler.decryptStream(SecurityHandler.java:449) ~[pdfbox-2.0.6.jar.6729965043262619269.tmp:2.0.6]
   at org.apache.pdfbox.pdfparser.COSParser.parseFileObject(COSParser.java:785) ~[pdfbox-2.0.6.jar.6729965043262619269.tmp:2.0.6]
   at org.apache.pdfbox.pdfparser.COSParser.parseObjectDynamically(COSParser.java:742) ~[pdfbox-2.0.6.jar.6729965043262619269.tmp:2.0.6]
   at org.apache.pdfbox.pdfparser.COSParser.parseObjectDynamically(COSParser.java:673) ~[pdfbox-2.0.6.jar.6729965043262619269.tmp:2.0.6]
   at org.apache.pdfbox.pdfparser.COSParser.parseDictObjects(COSParser.java:633) ~[pdfbox-2.0.6.jar.6729965043262619269.tmp:2.0.6]
   at org.apache.pdfbox.pdfparser.PDFParser.initialParse(PDFParser.java:241) ~[pdfbox-2.0.6.jar.6729965043262619269.tmp:2.0.6]
   at org.apache.pdfbox.pdfparser.PDFParser.parse(PDFParser.java:276) ~[pdfbox-2.0.6.jar.6729965043262619269.tmp:2.0.6]
   at org.apache.pdfbox.pdmodel.PDDocument.load(PDDocument.java:1000) ~[pdfbox-2.0.6.jar.6729965043262619269.tmp:2.0.6]
   at org.apache.pdfbox.pdmodel.PDDocument.load(PDDocument.java:956) ~[pdfbox-2.0.6.jar.6729965043262619269.tmp:2.0.6]
   at org.apache.pdfbox.pdmodel.PDDocument.load(PDDocument.java:904) ~[pdfbox-2.0.6.jar.6729965043262619269.tmp:2.0.6]
   at com.ubooquity.fileformat.pdf.b.a(SourceFile:34) ~[Ubooquity.jar:2.1.2]
   at com.ubooquity.b.d.a(SourceFile:62) ~[Ubooquity.jar:2.1.2]
   at com.ubooquity.data.feeder.a.b(SourceFile:531) ~[Ubooquity.jar:2.1.2]
   at com.ubooquity.data.feeder.a.b(SourceFile:468) ~[Ubooquity.jar:2.1.2]
   at com.ubooquity.data.feeder.a.b(SourceFile:112) ~[Ubooquity.jar:2.1.2]
   at com.ubooquity.data.feeder.a$$Lambda$5/16085064.run(Unknown Source) ~[na:na]
   at java.lang.Thread.run(Unknown Source) ~[na:1.8.0_231]

Just wanted to share the PDF OOM errors I'm seeing. I doubt it will help, but it can't hurt.