OpenCOBOL Master READ文のサンプルを試した (→COBOL - wikich）

■下記のエラーメッセージが永久ループ
libcob: READ and START not allowed (STATUS=47)
libcob: READ and START not allowed (STATUS=47)
libcob: READ and START not allowed (STATUS=47)
libcob: READ and START not allowed (STATUS=47)
libcob: READ and START not allowed (STATUS=47)
libcob: READ and START not allowed (STATUS=47)
libcob: READ and START not allowed (STATUS=47)
…

SELECT STATDATA ASSIGN TO "./data1.dat.txt"

上記のように拡張子にtxtをつけたらうまくいった