Migrating Oracle database to PostgreSQL

1. Migrating Oracle Database to
PostgreSQL

2. Topics Covered
• Why PostgresSQL
• Initial Discovery
• Migration Assessment
• Data Type Mapping
• Other Considerations
• PL/SQL Vs PLPGSQL
• Migration Plan
• Migration Challenges
Umair Mansoob

3. Why PostgreSQL
• Save money on license cost
• Save money on features like partitioning and high availability
• Save big money on support
• Substantial reduction of training + consulting costs
• Break free from vendor lock in
• Best in-class open source database
Umair Mansoob

4. Initial Discovery
• How much PL/SQL code reside in the Oracle database
• Define success criteria for migration
• Review application certification for PostgreSQL
• Review all Oracle database features in use
• Estimate cost and effort for migration
• Review Oracle data types & objects
• Check Database Size & Storage requirements
• Gather Performance requirements
Umair Mansoob

5. Migration Assessment
• Perform detail analysis of all data types used by Oracle database
• Review PL/SQL code in detail to estimate effort and cost for conversion
• Analyze possibility of migrating programming logic to application
• Analyze additional database features like compression, encryption and HA
• Creation detail migration plan with timeline
• Review existing application test plans for conversion
• Design comprehensive application testing plan for migration
Umair Mansoob

6. Data Type Mapping
Oracle PostgreSQL
VARCHAR2(n) VARCHAR(n)
CHAR(n) CHAR(n)
NUMBER(n,m) NUMERIC(n,m)
NUMBER(4) SMALLINT
NUMBER(9) INT
NUMBER(18) BIGINT
NUMBER(n) NUMERIC(n)
DATE TIMESTAMP(0)
TIMESTAMP WITH LOCAL TIME ZONE TIMESTAMPTZ
CLOB TEXT
BLOB RAW(n) BYTEA(1 GB limit) Large object
Umair Mansoob

7. Other Considerations
Oracle PostgreSQL
Dual Table In PostgreSQL, FROM clause is not mandatory so DUAL table is not necessary
SysDate In PostgreSQL there are multiple methods to get the date and time
Synonym CREATE SYNONYM is not supported in PostgreSQL
Sequence
There is a slight difference in the syntax of sequence in Oracle and
PostgreSQL.
Autonomous transaction Not supported
Externally organized tables Not supported
Transaction control PostgreSQL does not allow transaction control inside of PL/pgSQL
Oracle RAC No. A shared nothing architecture.
Oracle Data Guard PostgreSQL support Master-Master replication
Partition Tables Partitioning and sub-partitioning is supported but no interval partitioning yet
Umair Mansoob

8. PL/SQL Vs PLPGSQL
• PL/pgSQL is similar to PL/SQL in many aspects
• It is a block-structured, imperative language, and all variables have to be
declared.
• There is no PRAGMA statement in PostgreSQL.
• You cannot issue COMMIT in a PL/pgSQL function
• The show errors command does not exist in PostgreSQL, and is not needed
since errors are reported automatically.
• The type name varchar2 has to be changed to varchar or text.
Umair Mansoob

9. Migration Plan
Analyze Schema Data Code Test Cutover
Umair Mansoob

10. Migration Challenges
• Road for migration is not always smooth
• Migrating large data set ( Network Bandwidth )
• Porting PL/SQL Code to PostgreSQL
• Performance compression for critical application
• Minimize migration downtime
• Testing your applications is a huge part of the total effort in a
migration
• Training for your lead architects, DBAs, and developers
Umair Mansoob

11. Thank you.
Umair Mansoob
773-297-2061
umairmansoob@gmail.com