If you get a raise due to a general increase, a within grade increase, a promotion, change in jobs, move to a higher-paying locality, reclassification of a job to a higher level or for other reasons, your TSP investment will increase automatically if you are investing on a percentage of salary basis. If you are in the Federal Employees Retirement System, agency contributions will increase as well. Note: This does not apply if you get an award or some other form of payment that is not considered part of your basic pay.
If you are investing on a dollar amount biweekly basis, your investments will remain the same. In that case, you might want to consider increasing your investments—especially if you are in FERS (to capture higher agency contributions).