In the Database | Import | Import Table Data Wizard, after locating the spreadsheet and then clicking next to go to the "Preview File and Define Fields" section, it took over a minute or more to do so. The file is located on locally and the size of file does not matter. Opening the Windows task manager, the toad.exe process is at 100% cpu with memory usage jumping from the normal 75MBs to over 150MBs.
In addition, during the mapping the data section of the Import Table Data Wizard, the date format displays the date incorrectly, however the data is correct once its imported.
This problem only occurs when trying to import a spreadsheet that is in Excel 2007 format (Ext. .xlsx). When converting the same spreadsheet to a .xls or delimited text file format and retry, there are no performance problems
Convert the file to the .xls Excel file extension or a delimited text file.
Waiting for fix in a future release of Toad for Oracle.