Things stored in the first 25 bytes include page size, WAL status, and the file change counter. So at least part of the header there gets changed with every committed write transaction.
http://www.sqlite.org/fileformat2.html -----Original Message----- From: sqlite-users [mailto:sqlite-users-boun...@mailinglists.sqlite.org] On Behalf Of Deon Brewis Sent: Tuesday, February 06, 2018 11:57 AM To: SQLite mailing list Subject: [sqlite] Header corruption I’m trying to track down SQLITE corruptions that seems to corrupt our databases in a consistent way. (Running on 3.20.1). This isn’t related to a crash or hardware failure. The app is running and reading and writing to the database fine, and then suddenly we start getting a SQLITE_NOTADB errors. The first error we got was on trying to execute a ‘BEGIN TRANSACTION’, and everything thereafter started failing. When our database headers are fine, I see this: 00000000h: 53 51 4C 69 74 65 20 66 6F 72 6D 61 74 20 33 00 ; SQLite format 3. 00000010h: 10 00 02 02 00 40 20 20 00 00 10 9B 00 01 34 42 ; .....@ ...›..4B On corruption #1, I see this: 00000000h: 15 03 01 00 20 01 91 21 85 44 17 2C ED BE 21 FA ; .... .‘!…D.,í¾!ú 00000010h: 9E 74 E7 EA 9A 0A 15 2C 99 B0 B7 3B C6 F0 35 FB ; žtçêš..,™°·;Æð5û On corruption #2, I see this: 00000000h: 15 03 01 00 20 0F 1E CB B1 FF 9C 1E D0 D6 BB 22 ; .... ..˱ÿœ.ÐÖ»" 00000010h: 15 64 D3 F4 DD 38 FB DF A3 E0 47 B8 D7 F6 21 BC ; .dÓôÝ8ûߣàG¸×ö!¼ This bit pattern of “15 03 01 00” for the first 4 characters where it should be “SQLi” is a bit too much of a coincidence to ignore or write off as disk error. The rest of the header and file after the first 25-ish bytes or so, seem fine. It’s just these first 25 bytes that gets corrupted. If I restore Offsets 0 to Offsets 27 out of a “working” database, I get a usable file. Under what circumstances would SQLITE even attempt to re-write the header string? - Deon _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
