As has been mentioned UNIX filesystems are case sensitive. So a file named CASE_A2_B9.sas7bdat is not the same file as one named case_a2_b9.sas7bdat.
SAS on unix will only use lowercase letters in the names of files used to store SAS datasets. So if you run this program:
data copy;
set sasuser.CASE_A2_B9;
run;
It will look for a file name case_a2_b9.sas7bdat in the directory pointed to by the SASUSER libref.
Using a quoted physical name to reference the dataset in your SAS code will not help. If you write code like:
data copy;
set "~/sasuser/CASE_A2_B9.sas7bdat";
run;
Under the hood SAS will create a new libref pointing to the ~/sasuser/ directory and reference the dataset the same way as if you had use two level name to begin with.
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