[DoctorOhh]

Originally Posted by kovidgoyal

Hmm can't replicate that. To confirm, all you did was start calibre and repeatedly switch libraries?

Yes, that is exactly what I did. I use this bat file to run calibre.

Spoiler:

cd c:\
rmdir /s /q c:\Calibre_temp

REM Create new temp directory for this session.

cd c:\
mkdir Calibre_temp

REM Specify the location of the Calibre temp files
REM ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

SET CALIBRE_TEMP_DIR=C:\Calibre_temp

REM        CalibreRun.bat
REM        ~~~~~~~~~~~~~~
REM
REM Batch File to start a Calibre configuration on Windows
REM giving explicit control of the location of:

REM  - Calibre Config Files

REM Specify the location of the Calibre Config files
REM ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

SET CALIBRE_CONFIG_DIRECTORY=C:\My Dropbox\CalibreConfig

REM Location of calibre program files
REM ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

C:
CD \Program Files\Calibre2

REM Display settings that will be used
REM ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

echo CONFIG=%CALIBRE_CONFIG_DIRECTORY%

REM  The following gives a chance to check the settings before
REM  starting Calibre.  It can be commented out if not wanted.

echo "Press CTRL-C if you do not want to continue"
pause

REM Start up the calibre program.
REM ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
REM

start calibre.exe --start-in-tray

Update:

• Memory initial load of 12500 book library - 173M
• Memory after 1st switch to 5000 book library - 207M
• Memory after 2nd switch back to 12500 book library - 319M
• Memory after 3rd switch back to 5000 book library - 354M
• Memory after 4th switch back to 12500 book library - 456M