To do this, define a custom format using workbench which can read the schema, search for the schema attribute fme_data_type with values of fme_decimal and change them to varchar.   (Explode the schema list coming from the schema reader, string search for value of fme_decimal in fme_data_type, create a new attribute fme_data_type with value varchar and rebuild list)

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The custom format is then used as a workspace resource in the translation workspace which converts from CSV to SDE_Geodatabase.

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