Database migration Oracle to PostgreSQL, domain indexes
INDEXTYPE IS CTXSYS.CTXCAT is Oracle's way of defining a "full text index" on a column -- as opposed to an ordinary B-tree.

The good news is that Postgres also has full text indexes, and these are documented extensively at https://www.postgresql.org/docs/current/static/textsearch.html

The basic syntax for creating a similar index in Postgres is

create index CTX_IDX_UFA_EMAIL
on USR_ACCOUNT
using gin (to_tsvector('english', EMAIL));


The bad news for you is that substituting this type of index in the database will mean you also need to change the queries on this column/table. This may or may not also have implications for the user interface -- it could be that end users are currently able to enter search terms that are understood by the Oracle full text index searching implementation.