On UNIX, you may also use the IQDSN utility to create Oracle DSNs.
iqdsn -w data-source-name -or -c configuration-options
For example:
iqdsn -w MyOracleDSN -or -pe -c Userid=dba;Password=sql;SID=abcd;ArraySize=100000;ProcResults=y;enableMSDIC=n
For example:
iqdsn -w MyOracleDSN -or -pe -c Userid=dba;Password=sql;SID=abcd;ArraySize=100000;ProcResults=y;enableMSDIC=n