It's in the ReadMe for 8.5:
4.1 New ars.cfg parameter ARS_ORIGINAL_CODEPAGE
A new ars.cfg parameter, ARS_ORIGINAL_CODEPAGE, is now required.
When using OnDemand for MP V8.5 to access a pre-V8.5 OnDemand instance,
this MUST be set to the codepage the pre-V8.5 OnDemand server was
running in. Failure to set it will prevent the OnDemand server from
starting. Setting it incorrectly will result in data corruption.
Example failure to start message which will be sent to the console:
DB Error: STARTUP -- SQLSTATE=1. ARS_ORIGINAL_CODEPAGE is not
defined in ars.cfg. Run arsdb -u -I <OD_INSTANCE> to
determine setting of ARS_ORIGINAL_CODEPAGE, SQLCODE=0,
File=arssrvr.c, Line=7892
4.2 Steps to set the value of ARS_ORIGINAL_CODEPAGE
4.2.1 UNIX Servers
Run arsdb -u without ARS_ORIGINAL_CODEPAGE in the ars.cfg for
information on the proper setting for ARS_ORIGINAL_CODEPAGE.
An example of running the arsdb -u -I <OD_INSTANCE> command without
ARS_ORIGINAL_CODEPAGE in the ars.cfg is:
arsdb: Unable to initialize environment. The return code is -1. If
this is a new (created in 8.5) instance, then define
ARS_ORIGINAL_CODEPAGE=819 in ars.cfg. Otherwise, if this is
an existing instance (created prior to 8.5), then define
ARS_ORIGINAL_CODEPAGE=923 in ars.cfg. Once set,
ARS_ORIGINAL_CODEPAGE must never change.
