為何打開dbase 的***.dbf檔案會產生index not found 的問題(編號：3444)

為何打開dbase 的***.dbf檔案會產生index not found 本人 source
code 如下
Dim db1 As New ADODB.Connection
　Dim rs1 As New ADODB.Recordset

db1.CursorLocation = adUseClient
　db1.Open "PROVIDER=MSDASQL;dsn=dbf;uid=;pwd=;"
　sql = "select * from pabdb02m"
　rs1.Open sql, db1, adOpenKeyset, adLockOptimistic

跑到最後一行時會產生index not found