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If you're an active trader and your current investment account has many transactions pertaining to sold securities you may want to consider this:
Archive Investment Transactions
For about a year now, a new function has been available in Quicken, Archive Transactions. It will split your investment account register into two parts, leaving only those securities' transactions where you currently hold >0 shares in the active register. The rest is moved to a new Archive register within the current data file.
Having less transactions in your active register might improve performance.
Please read and carefully follow instructions here: https://www.quicken.com/support/how-archive-investment-transactions Eventually, after a couple of years, you might consider splitting your data file in two, using Year End Copy, with all the archived investment transactions in the old file and none remaining in the active file.