Oracle - MySQL Migration• Cluster Technical Leader at Pythian for MySQL technology • Previous manager Professional Service South EMEA at MySQL/SUN/ Oracle • In MySQL before the

Oracle - MySQL Migration

Marco Tusa

MySQL CTL

MySQL Conference 12 April 2012

© 2012 Pythian 2

Why Companies Trust Pythian

• Recognized Leader: • Global industry-leader in remote database administration services and consulting for Oracle, Oracle Applications, MySQL and SQL Server • Work with over 150 multinational companies such as Toyota, Fox Sports, and MDS Inc. to help manage their complex IT deployments

• Expertise: • One of the world’s largest concentrations of dedicated, full-time DBA expertise.

• Global Reach & Scalability: • 24/7/365 global remote support for DBA and consulting, systems administration, special projects or emergency response

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• Recognized Leader: • Global industry-leader in remote database administration services and consulting for Oracle, Oracle

Applications, MySQL and SQL Server

• Work with over 165 multinational companies such as Forbes.com, Fox Sports, Nordion and Western Union to help manage their complex IT deployments

• Expertise: • One of the world’s largest concentrations of dedicated, full-time DBA expertise. Employ 7 Oracle

ACEs/ACE Directors

• Hold 7 Specializations under Oracle Platinum Partner program, including Oracle Exadata, Oracle GoldenGate & Oracle RAC

• Global Reach & Scalability: • 24/7/365 global remote support for DBA and consulting, systems administration, special projects or

emergency response

Why Pythian

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Who am I? • Cluster Technical Leader at Pythian for MySQL technology

• Previous manager Professional Service South EMEA at MySQL/SUN/Oracle

• In MySQL before the SUN gets on us

• Lead the team responsible for Oracle & MySQL DBs service in support to technical systems, at Food and Agriculture Organization of United Nations (FAO of UN)

• Lead developer & system administrator teams in FAO managing the Intranet/Internet infrastructure.

• Worked (a lot) in developing countries like (Ethiopia, Senegal, Ghana, Egypt …)

• My Profile http://it.linkedin.com/in/marcotusa

• Email [email protected] [email protected]

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I like to start from :* • Scalability and Flexibility

• High Performance

• High Availability

• Robust Transactional Support

• Web and Data Warehouse Strengths

• Strong Data Protection

• Comprehensive Application Development

• Management Ease

• Open Source Freedom and 24 x 7 Support

• Lowest Total Cost of Ownership *http://www.mysql.com/why-mysql/topreasons.html

Why MySQL

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MySQL TCO Savings Calculator (now)*

*From www.mysql.com TCO calculator

Why MySQL?

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Why MySQL?

MySQL TCO Savings Calculator (before)

*From www.mysql.com TCO calculator ancient time

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Why MySQL?

All good then? When should I migrate my environment to MySQL?

Cost is not the only aspect to consider:

• Need to use MySQL correctly;

• Be aware of existing issues

• good list of them from Baron*

• Identify the real effort require for the migration.

*http://www.xaprb.com/blog/2009/03/13/50-things-to-know-before-migrating-oracle-to-mysql/

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12 things to know about MySQL (1) 1 Subqueries are poorly optimized (optimization expected in 5.6 http://dev.mysql.com/doc/

refman/5.6/en/from-clause-subquery-optimization.html)

2 There is limited ability to audit (no user reference unless General log active).

3 Authentication is built-in. There is no LDAP, Active Directory, or other external authentication capability. (New PAM module available for 5.5 but only enterprise)

4 Data integrity checking is very weak, and even basic integrity constraints cannot always be enforced. (replication)

5 Most queries can use only a single index per table; some multi-index query plans exist in certain cases, but the cost is usually underestimated by the query optimizer, and they are often slower than a table scan.

6 Foreign keys are not supported in most storage engines.

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12 things to know about MySQL (2) 7 Execution plans are not cached globally, only per-connection.

8 There are no integrated or add-on business intelligence, OLAP cube, etc packages.

9 There are no materialized views (also if we can use Event scheduler)

10 Replication is asynchronous and has many limitations and edge cases.

11 DDL such as ALTER TABLE or CREATE TABLE is non-transactional. It commits open transactions and cannot be rolled back or crash-recovered.

12 Each storage engine can have widely varying behavior, features, and properties. (positive and negative)

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Prepare a plan, and do not improvise

• Analyze the source (from application to data design)

• Identify show stoppers

• Identify how to map what to what

• Identify how to organize the target

Most important: Be ready to do not force migration. If it does not make sense to proceed, STOP!

Getting Started?

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The Motto

Use the right tool for the job

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• Database is used only to store data all the logic reside in the application

• Database contains logic such as stored procedure and complex package

• Database containing data for data warehouse

• Real time data and historical records (telephone company)

Most common source cases

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Define the process

Analyze

Understand

Match Src/dest

Re/Design Extract src

Convert

Import Schemas data Logic

Partition Index Test/POC Validate

Som

ethi

ng

fails

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When analyzing the source database(s) what should be the outcome?

• Easy to understand excluding list

• Identify Source type (Simple data move; data + Intelligence; data mart)

• In detail review per schema of complexity

• Detailed assessment of modification and effort database objects

• Detailed assessment of functions/functionalities used (also in the

application)

• Application assessment and review

Mitigating risk of failure (analyze)

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Easy to understand excluding list

• Create a rank on the “impedance“ o Apply it to analyzed schema i.e.:

*The lower grade the better


Issue Workaround Grade* Notes Reference to external schemas in the a different instance (db link)

10 Not portable

… Packages See Writing stored procedures 9 Require full recode

Procedures See Writing stored procedures 9 Require full recoding

Unique key longer then 255 characters See Key length limitations 4

Views alias Manually added 4 Columns alias must be added manually

Sequences See Migration of Sequences 3 Whenever possible convert to autoincrement

Empty schemas See empty schema definitions 2 Convert to User definition

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1. Identify and understand differences - Oracle vs MySQL behavior - DDL differences MySQL – Oracle - DML differences - Data formatting and encoding - Data set dimensions

2. Identify and understand business logic differences - map Oracle functions to MySQL - convert Oracle logic to MySQL (if possible)

3. Realize a Proof of Concept - involve an experienced Oracle DBA - involve an experience MySQL DBA - involve the developers - use real data - use real traffic


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Understanding server behavior Identify different behavior between Oracle and MySQL, some basic differences (cont.)

• Oracle is case insensitive in the schema object definition while MySQL is case sensitive (remember to set lower_case_table_names)

• Oracle does not provide DEFAULT value for NOT NULL, MySQL does.

• Oracle supports millisecond MySQL only from 5.6

• Oracle does not apply silent conversion to data types MySQL does (set sql_mode)

• Oracle maximum VARCHAR2 dimension is 4,000 bytes, MySQL 65,535

Mitigating risk of failure (understand)

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Understanding server behavior Identify different behavior between Oracle and MySQL, some basic differences 1. what is what, understanding the naming conventions AUTO COMMIT Default enabled in MySQL

- you can't ROLLBACK - Non Transactional Storage Engines - SET AUTOCOMMIT = {0 | 1};

2. securing the database Database Authentication/Privileges - MySQL Privileges (local; no roles) - Oracle System Privileges (local/external; roles)

3. Dual in MySQL is not required - e.g. SELECT 1+1 but we provided for Oracle Compatibility - SELECT 1+1 FROM DUAL - SELECT CURRENT_USER() FROM DUAL


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Understanding DDL differences Key length limitations

Oracle handles index with a length up to the 40%(plus some overhead) of the database block size (db_block_size), this could be a problem with MySQL.

MySQL can use 767/1000 bytes as a primary key or an index.

But because in UTF-8, one character is 3 bytes, a primary key or any key can be at most 255 characters.

Work around only for InnoDB innodb_large_prefix in case of Dynamic/Compressed ROW format.


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Understanding DDL differences autoincrement/sequence

Oracle uses sequence, while MySQL is bound to AUTO_INCREMENT

AUTO_INCREMENT must be NOT NULL and part of the primary key

Oracle can retrieve sequence values MySQL need to use the function LAST_INSERT_ID().

The LAST_INSERT_ID() is maintained per connection and is thus safe for concurrent use.

Do not use “SELECT MAX(id)+1 FROM tab”


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Understanding Function Triggers difference

Procedure and triggers difference

• one trigger for event in MySQL, all the different actions needs to be group

• no packages, workaround using a fake schema

• different behavior by storage engine and if transactional or not

• Security assignments and security definer/invoker

• Up to 5.5 very basic error handling and lack of “signal” . So version 5.5 is almost

mandatory if in the need to use decent error handling.


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Understanding DDL differences Identify conversion between Oracle and MySQL for • Tables • Views • Procedures • Functions • Packages • Triggers • Sequences, synonyms etc. I.e. data types:

Mitigating risk of failure (match)

MySQL Data Type Oracle Data Type

BIGINT NUMBER(19, 0)

BIT RAW BLOB BLOB, RAW CHAR CHAR DATE DATE DATETIME DATE DECIMAL FLOAT (24) DOUBLE FLOAT (24)

DOUBLE PRECISION FLOAT (24)

ENUM VARCHAR2 FLOAT FLOAT

MySQL Data Type Oracle Data Type INT NUMBER(10, 0) INTEGER NUMBER(10, 0) LONGBLOB BLOB, RAW LONGTEXT CLOB, RAW MEDIUMBLOB BLOB, RAW MEDIUMINT NUMBER(7, 0) MEDIUMTEXT CLOB, RAW NUMERIC NUMBER REAL FLOAT (24) SET VARCHAR2 SMALLINT NUMBER(5, 0) TEXT VARCHAR2, CLOB TIME DATE TIMESTAMP DATE TINYBLOB RAW TINYINT NUMBER(3, 0) TINYTEXT VARCHAR2 VARCHAR VARCHAR2, CLOB YEAR NUMBER

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Understanding DML differences 1. Join syntax 2. SQL_mode 3. Data comparison using collation 4. other common differences

• SQL macro differences • NVL() --> IFNULL() • ROWNUM --> LIMIT • SEQ.CURRVAL --> LAST_INSERT_ID() • SEQ.NEXTVAL --> NULL • NO DUAL necessary (SELECT NOW()) • NO DECODE() --> IF() CASE() • JOIN (+) Syntax --> INNER|OUTER LEFT|RIGHT • No Hierarchical (connect to prior)

Mitigating risk of failure (match)

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Data export & Index redesign

• Re-organize the schema/table not just convert data types

• Storage engines

• Index full redesign

• Data organization

• Sharding

• Partition

• Logic rewrite

• Inside MySQL

• Move to application

Mitigating risk of failure (convert)

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Realize a Proof of Concept

Don’t work Alone

Involve Oracle experienced DBA

Involve MySQL experience DBA

Involve the developers

Use real data

Use real traffic

Take one source for each type; start with the easy one

Go Back to the analysis phase if you have to

Mitigating risk of failure (POC)

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General document

• Description of the main differences between platforms

• Description of the work around found

• Explanation of what to do to avoid most common issues

• Code write instructions

• Common function mapping

• List of the blocking issue(s)

• List and explanation of what cannot be migrated and why

What should my migration doc contains?

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Per schema document

• Overview of the effort for the migration


Schema Name: Test

Objects Number Time(min) hrs Cost(0,50 cent/min) Table 200 320 5,3 2,65 Views 50 5 0,08 0,04

Procedure 500 5000 83,33 41,67 Function 12 200 3,33 1,67 Trigger 200 2500 41,67 20,83 Package 3 5 0,08 0,04 Total Time 8030 133,80 66,90

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Per schema document

• Effort per table like:


Schema Name: Test Table City Rows 2000 Estimated min 10 Attribute Data type source dim source Data type dest dim dest Name VARCHAR2 50 varchar 50 lat FLOAT FLOAT long FLOAT FLOAT population Number 10,0 INT 10 SqKm Number 7,0 MEDIUMINT Country CHAR 3 CHAR 3

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Trigger section

• Effort per schema

• Effort per Table:


Schema Name: Test

Events Before Time(min) After Time(min) Insert 50 600 20 300 Update 50 600 20 300

Delete 50 600 10 100 Total 150 50 Packages 3 3 Total Time 1800 700

Schema Name: Test Table Total 24 action time Trigger name Source Insert* Update* Delete* Trigger name dest Before

Ins_change_ID 20 Ins_actions Ins_change_ISO 10 upd_population 15 upd_population

After del_died_male 10 del_died_male avr_pop_calculation 15 avr_pop_calculation

Total 30 30 10 *time in minutes for conversion

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Procedure - function section

• Effort per schema

• Effort per Table:


Schema Name: Test

Package Number Time(min) Cost(0,50 cent/min) Pack1 112 1200 Pack2 200 2000

Pack3 200 2000 Total 521 Packages 3 Total Time 5200

Schema Name: Test Table Total 3 Procedure name Code rows Impedance** Time* Packge comments Proc_1 200 4 480 Pckg1 Complex Error handling Func_1 50 0 120 Pckg2 No problem Proc_2 300 10 - Pckg1 Use of connect by prior

Total 600 *time in minutes for conversion ** The lower the better 10 means no portable

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Document from the Proof of Concept per source type

• Expected results • Real value from test • Issues found • Work around identify • Time/Effort per schema

• Breakdown per object (Table, View, Trigger, SP) • Redefine expectations • Review efforts and costs

• Be ready to drop something from the migration list


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No! there are tools on the market but:

• Choose your product carefully !

• Better a simple one than something too complex

• Always double check before applying

• Nothing will replace human/professional knowledge/experience

Should I do all this manually?

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Mentioning some of many.

I still like to play with OLD MySQL migration Toolkit, I did a lot of successful work around the java classes.

Off the shelf: http://dbconvert.com/convert-oracle-to-mysql-pro.php http://www.talend.com/index.php http://www.ispirer.com/products

However nothing can replace knowledge, and good planning.

Tools

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Documents

Oracle - MySQL Migration• Cluster Technical Leader at Pythian for MySQL technology • Previous manager Professional Service South EMEA at MySQL/SUN/ Oracle • In MySQL before the