Search notes:

%UserProfile%\Documents\My Data Sources

This folder is opened, among others(?), in Excel through Data -> Get & Transform Data -> Existing Connections -> Browse for more.
After installing Windows or a new user, this folder seems to contain four files:
The initial(?) content of ~+Connect to New Data Source.odc~ is 
<html>
<head>
<meta http-equiv=Content-Type content="text/x-ms-odc; charset=utf-8">
<meta name="ProgId" content="ODC.New">
<meta name="SourceType" content="NewOLEDB">
</head>
</html>
The initial(?) content of ~+NewSQLServerConnection.odc~ is 
<html>
<head>
<meta http-equiv=Content-Type content="text/x-ms-odc; charset=utf-8">
<meta name="ProgId" content="ODC.New">
<meta name="SourceType" content="NewSQLServer">
</head>
</html>

Index

Fatal error: Uncaught PDOException: SQLSTATE[HY000]: General error: 8 attempt to write a readonly database in /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php:78 Stack trace: #0 /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php(78): PDOStatement->execute(Array) #1 /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php(30): insert_webrequest_('/notes/Windows/...', 1758201191, '216.73.216.150', 'Mozilla/5.0 App...', NULL) #2 /home/httpd/vhosts/renenyffenegger.ch/httpsdocs/notes/Windows/dirs/Users/username/Documents/My-Data-Sources/index(58): insert_webrequest() #3 {main} thrown in /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php on line 78