SQL Error: OA-12991 - Unable to Drop a Column after removing all referenced Multi-Column constraints
Setup:

create table t3 (c1 number, c2 number);
alter table t3 add  supplemental log group sl1 (c1, c2) always;
alter table t3 add constraint t3_uk unique (c1, c2);
insert into t3 values (1, 2);
commit;


Try to drop the column:

SQL&gt; alter table t3 drop column c2;
alter table t3 drop column c2
                           *
ERROR at line 1:
ORA-12991: column is referenced in a multi-column constraint


So far so good, goes as expected. Drop the constraint:

SQL&gt; alter table t3 drop constraint t3_uk;

Table altered.

SQL&gt; alter table t3 drop column c2;
alter table t3 drop column c2
                           *
ERROR at line 1:
ORA-12991: column is referenced in a multi-column constraint


Still doesn't work, same error. Check the supplemental log group:

select * from user_log_groups where table_name = 'T3'

OWNER LOG_GROUP_NAME TABLE_NAME LOG_GROUP_TYPE      ALWAYS      GENERATED
----- -------------- ---------- ------------------- ----------- --------------
BP    SL1            T3         USER LOG GROUP      ALWAYS      USER NAME


Drop the supplemental log group, then try dropping the column again:

SQL&gt; alter table t3 drop supplemental log group sl1;

Table altered.

SQL&gt; alter table t3 drop column c2;

Table altered.