Message viewer 'Source' and 'Target' drop down menus very slow

This is embarrassing. I should know how to do this but I have forgotten.

I know the slowness of the 'Source' and 'Target' parameters in Message message viewer being slow to load is caused by the Bitmap indices of Ens.MessageHeader.

I know I need to run the 'bitmap index clean up' routine for Ens.MessageHeader to fixed the issue.

 What I forget is how to do this? 

https://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY...

Any advice or suggestions appreciated.

Kind regards, 

Stephen