Connect to data with sys user sqlplus:
Sql*plus:release 11.2.0.3.0 Production on Thu June 22 11:07:58 2017
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Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0-64bit Production
With the partitioning, Oracle Label Security, OLAP, Data Mining,
Oracle Database Vault and Real application testing options
Sql> Show parameter Sec_case_sensitive_logon;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
Sec_case_sensitive_logon Boolean TRUE
sql> ALTER SYSTEM SET sec_case_sensitive_logon = FALSE;
The system has changed.
Sql> Show Parameter Sec_case_sensitive_logon
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
Sec_case_sensitive_logon Boolean FALSE
Sql>
See if the passwords for Oracle 11g database users are case sensitive