In the Ledger company profile on the Posting/Reports tab is an option called 'Auto build TX inquiry index'. With this enabled, the transaction lookup file (referred to by Steve in his reply) is rebuilt every time you post a batch. With this disabled, posting a batch will delete this file, and accessing the lookup function (either in Transaction inquiry or the Financial Reporter drill-down) will start to regenerate the index file.

This does not change any of the replies above if an account was consolidated.