Yes DB size is around 1TB , in which probably more then 1k tables and same indices persist. others objects such as SP,SF and Triggers are also good in numbers . It's not HA solution .
I have been assigned to migrate the ingress database to PostgreSQL database. Can anyone help me with the tools or the strategy we should follow to do so?
You've not mentioned how big the source database is, nor how many tables, indices, triggers, stored procedures, stored functions, etc, nor whether the Ingres instance uses any High Availability features.
Converting the triggers and stored procedures/functions will be the biggest hurdle. The CREATE TABLE and CREATE INDEX statements will probably have minor syntax differences that "sed" might be able to fix. (Presumably Ingres has a feature to dump the database's schema into a set of CREATE TABLE, CREATE INDEX, CREATE ... statements?)
CSV is of course the lowest common denominator for file transfer, and you want to create everything except the plain tables after loading the data into PG tables. And don't forget parallelism when unloading and loading data.