SQL> connect thiru/****
Connected.

-- these are the tables in this schema
SQL> select table_name from user_tables;

TABLE_NAME
------------------------------
DEPT
EMP
GTT
T1
T2
T3
TC
TIMESTAMP_T
T_TEMP

-- create 'customer' user for read only access. This needs to be done as a user with DBA privileges.

SQL> create user customer identified by customer default tablespace users temporary tablespace temp;

User created.

-- Grant him privileges to connect to Oracle and create private synonyms

SQL> grant create session,create synonym to customer;

Grant succeeded.

-- Grant him Select access on a couple of tables. You can also create a role , grant privileges to the role and then grant the role to the customer user, for easier privilege management. 

SQL> grant select on thiru.dept to customer;

Grant succeeded.

SQL> grant select on thiru.emp to customer;

Grant succeeded.

-- Login as your Customer user

SQL> connect customer/customer;
Connected.

-- Select one of application tables

SQL> select count(*) from thiru.dept;

  COUNT(*)
----------
         4

-- For transparency, you can create synonym for this table, in customer's schema

SQL> create synonym dept for thiru.dept;

Synonym created.

-- Query Thiru's dept table ,using the synonym

SQL> select * from dept;

    DEPTNO DNAME          LOC
---------- -------------- -------------
        10 ACCOUNTING     NEW YORK
        20 RESEARCH       DALLAS
        30 SALES          CHICAGO
        40 OPERATIONS     BOSTON

-- but customer cannot delete from the table

SQL> delete from dept;
delete from dept
            *
ERROR at line 1:
ORA-01031: insufficient privileges

create user customer identified by customer default tablespace users temporary tablespace temp
*
ERROR at line 1:
ORA-00959: tablespace 'USERS' does not exist

create user customer identified by customer default tablespace tbs_data temporary tablespace tb_temp

grant select on tcpos.tb_articles to test
                      *
ERROR at line 1:
ORA-01031: insufficient privileges