>We recently updated the VFP9 from VFP6 and we found program which compiled with VFP9 are slower than VFP6 or VFP7.
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>Mainly data manipulation takes longer time period in VFP9 comparing with other version of VFP. Please let me know is there any particular reason behind this and how to overcome this problem.

This is most likely because a bug was fixed in VFP9 which in earlier versions could give you wrong results. CPDBF() for all your tables must match CPCURRENT(), or Rushmore optimation is turned off.