Because the backup groups several table rows for efficiency, large pages can cause a transaction to be too big to handle.
This can be fixed.
In admin/db_backup.php, about lines 230-240 (depending on version), you will find:
Code: Select all
// HERE WE CONTROL THE SIZE OF $vals --- LIMIT INSERTS TO // 15000 ROWS, 1500 ROWS FOR THE `links` TABLE if ($z == 15000 || (substr($table, strlen($table)-5) == "links" && $z == 1500)
Where you see "&& $z == 1500)", reduce the "1500" to a smaller number. Keep reducing the number until a backup completes. I've seen it necessary to go to as low as 15 for some very large pages. It is theoretically possible to have pages so large that even that won't work. Then the only solution would be to reduce page size.