This controls whether CREATE TABLE and CREATE TABLE AS include an OID column in newly-created tables, if neither
WITH OIDS nor
WITHOUT OIDS is specified. It also determines whether OIDs will be included in tables created by SELECT INTO. The parameter is
off by default; in PostgreSQL 8.0 and earlier, it was
on by default.
The use of OIDs in user tables is considered deprecated, so most installations should leave this variable disabled. Applications that require OIDs for a particular table should specify
WITH OIDS when creating the table. This variable can be enabled for compatibility with old applications that do not follow this behavior.