The April PSU for Oracle Databases is available sind 19th July 2016.

There is a risk that you'll get a warning when you try to install the patch with opatch:

[Jul 20, 2016 10:48:52 AM] OUI-67200:Make failed to invoke "/usr/bin/make -f ins_odbc.mk isqora ORACLE_HOME=/u01/app/oracle/product/12.1.0.2/ee"....'/usr/bin/ld: cannot find -lodbcinst
collect2: ld returned 1 exit status
make: *** [/u01/app/oracle/product/12.1.0.2/ee/odbc/lib/libsqora.so.12.1] Error 1
'
[Jul 20, 2016 10:48:52 AM] Stack Description: java.lang.RuntimeException: /usr/bin/ld: cannot find -lodbcinst
collect2: ld returned 1 exit status
make: *** [/u01/app/oracle/product/12.1.0.2/ee/odbc/lib/libsqora.so.12.1] Error 1

[Jul 20, 2016 10:49:08 AM] The following warnings have occurred during OPatch execution:
[Jul 20, 2016 10:49:08 AM] 1) OUI-67200:Make failed to invoke "/usr/bin/make -f ins_odbc.mk isqora ORACLE_HOME=/u01/app/oracle/product/12.1.0.2/ee"....'/usr/bin/ld: cannot find -lodbcinst
collect2: ld returned 1 exit status
make: *** [/u01/app/oracle/product/12.1.0.2/ee/odbc/lib/libsqora.so.12.1] Error 1
'
[Jul 20, 2016 10:49:08 AM] 2) OUI-67124:Re-link fails on target "isqora".
[Jul 20, 2016 10:49:08 AM] --------------------------------------------------------------------------------
[Jul 20, 2016 10:49:08 AM] OUI-67008:OPatch Session completed with warnings.

It seems that you need to install unixODBC and unixODBC-devel RPM package to solve that issue. More information can be found in the MOS Note 2163593.1.