I have faced weird errors if a file was not closed, especially if it is further utilized in the process, therefore it is advisable to close the file explicitly using the close command. Per SAS documentationy default, a file is opened with a control level of RECORD. OPEN defaults to the strongest access mode available in the engine. That is, if the engine supports random access, OPEN defaults to random access. Otherwise, files are opened with sequential access, and a system-level warning is set. If you do not close the file, it remains in the memory and may cause issues if it is utilized again in the same macro, but If you open a file within a DATA step, it closes automatically when the DATA step ends.
Hope this helps!
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