How to Migrate from Postgres to Oracle in PostgreSQL

How do I migrate a PostgreSQL database to Oracle without data loss?

Move schema and data from a PostgreSQL database to Oracle while preserving structure, constraints, and data integrity.

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Description

Why migrate from PostgreSQL to Oracle?

Teams switch when they need Oracle’s advanced RAC clustering, built-in partitioning, or tight integration with existing enterprise tooling. Understanding the exact business driver guides tooling choices and testing plans.

Which tools work best for Postgres→Oracle?

ora2pg auto-converts DDL and exports data, Oracle SQL Developer has a Migration Wizard, and custom scripts handle edge cases. Start with ora2pg, then patch remaining objects manually.

What is the high-level migration workflow?

1) Assess objects with ora2pg’s -a report. 2) Generate Oracle-friendly DDL. 3) Export data to flat files or direct INSERT statements. 4) Load into Oracle with SQL*Loader or SQLPlus. 5) Validate row counts and constraints.

How do I prepare the PostgreSQL schema?

Normalize identifiers to lower case, replace SERIAL with explicit sequences, and convert JSONB to CLOB or XML. Resolve reserved words like ORDER by quoting or renaming.

How do I run ora2pg?

Edit ora2pg.conf, setting PG_DSN, ORACLE_DSN, SCHEMA, and EXPORT_SCHEMA. Use -t for object type, -o for output file, and -b for data directory. Run assessments early to reveal blockers.

How is data loaded into Oracle?

For large tables, create CSV with COPY then use SQL*Loader: sqlldr userid=user/pass control=customers.ctl. Small tables migrate quickly with generated INSERT ALL statements from ora2pg.

How do I verify the migration?

Compare row counts, checksums, and spot-check monetary columns. Run application test suites against the Oracle instance. Disable production writes on Postgres during the final sync window.

Best practices for smooth migration

Create repeatable scripts, version control the generated DDL, and run multiple dry-runs. Automate sequence value updates with SELECT setval() equivalents in Oracle.

Common pitfalls to avoid

Ignoring byte-ordering differences in BYTEA fields causes corrupt blobs. Forgetting to migrate triggers breaks business rules. Always map TIMESTAMPTZ to Oracle TIMESTAMP WITH TIME ZONE.

When should I switch production traffic?

Only after automated tests, performance benchmarks, and read-only user acceptance testing pass. Use application feature flags for instant rollback if issues surface.

Why How to Migrate from Postgres to Oracle in PostgreSQL is important

How to Migrate from Postgres to Oracle in PostgreSQL Example Usage


-- Verify monetary totals after migration
SELECT SUM(total_amount) AS pg_total
FROM Orders@postgres_dblink
UNION ALL
SELECT SUM(total_amount) AS oracle_total
FROM Orders;

How to Migrate from Postgres to Oracle in PostgreSQL Syntax


-- 1. Generate Oracle-ready DDL for specific ecommerce tables
ora2pg -t TABLE -i Customers,Orders,Products,OrderItems \
       -o ecommerce_ddl.sql -b /tmp/out -p

-- 2. Export data from PostgreSQL as CSV
COPY Customers TO '/tmp/out/customers.csv' WITH CSV;
COPY Orders    TO '/tmp/out/orders.csv'    WITH CSV;

-- 3. Create SQL*Loader control file (customers.ctl)
LOAD DATA
INFILE 'customers.csv'
INTO TABLE Customers
FIELDS TERMINATED BY ','
(id, name, email, created_at "to_date(:created_at,'YYYY-MM-DD HH24:MI:SS')")

-- 4. Load into Oracle
sqlldr userid=ecom/ecompass control=customers.ctl DIRECT=TRUE

-- 5. Validate counts
SELECT COUNT(*) FROM Customers;

Common Mistakes

Mismatch of data types like JSONB → CLOB. Fix by explicitly casting problematic columns and updating the ora2pg type mapping.
Forgetting to migrate sequences, leading to PRIMARY KEY collisions. Always export sequences and reset Oracle identity columns to the max existing value.