Collaborate 2012 - Administering MySQL for Oracle DBAs

Administering MySQL for
Oracle DBAs

Eng. Nelson Calero, OCP
UYOUG

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Administering MySQL for Oracle DBAs

About me:

http://www.linkedin.com/in/ncalero
Working with Oracle tools and Linux environments since 1996
DBA Oracle (since 2001) & MySQL (since 2005)
Oracle University Instructor since 2011
Co-founder and President of the Oracle user Group of Uruguay
(UYOUG) since 2009
Computer Engineer. OCP DBA 10g

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AGENDA

1 – Brief Intro to main MySQL architectural components
2 – Comparison Oracle vs MySQL
3 – Installation and Upgrades
4 – Security & auditing
5 – Performance management
6 – Backup & Recovery
7 – Designing for High Availability

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1 - Introduction to the
MySQL architecture

http://dev.mysql.com/doc/refman/5.5/en/pluggable-storage-overview.html 6/54

MySQL architecture

MySQL server
• comes in a Community and Enterprise Edition
• has many databases
• no schemas
• two OS processes when running: mysqld and mysqld_safe
• listen on port tcp/ip 3306 by default
• local connections use sockets (similar to beq in Oracle)
• creates one thread per each client connection
• thread pool is a commercial feature of 5.5.16 (Oracle shared server)
• cost based optimizer
• replication is not transactional
• cluster is another product, with shared nothing architecture

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MySQL architecture

binaries
• installed in /usr/bin if using RPM installation on most *nix
• if using binary distribution (.tar), can be placed in custom directories
• Is the way of having different versions on same server

No OFA or similar.

Startup script (/etc/init.d/mysql) has some defaults, changed by configuration
file (/etc/my.cnf)
datadir: /var/lib/mysql
bindir: /usr/bin

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MySQL architecture

Internal components

•memory caches
{ query | innodb buffer | innodb log | myisam key | user | dictionary } cache

• InnoDB undo log - rollback segments
•splitted as insert undo and update undo buffer
•part of the system tablespace by default
•since MySQL 5.6 can be moved: innodb_undo_tablespaces

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1 - MySQL architecture
Internal components

Storage engines:
pluggable architecture that enables different algorithms for handling data.

InnoDB – Transactional. Default from 5.5
MyISAM – non transactional. Default before 5.5
Memory – stored only in memory, not persisted to disk
NDB – used by the Cluster
Archive/Blackhole/Merge/Federated - other specific use engines

Many third parties implementations
XtraDB – from Percona. InnoDB improved

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Internal components

Storage engine files

• table.frm – table definition, regardless of storage engine used ($datadir/dbname)
• InnoDB logs – transactional log, used for crash recovery (ib_logfile1)
• 2 by default. Circular rotation. No archiving
• InnoDB system tablespace – ibdata1
• Stores all data and metadata by default
• Can be changed to external tablespaces: innodb_file_per_table in my.cnf
• Stores each table data in one file named table.ibd
• other tablespaces – used by NDB similarly as Oracle.

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Internal components

Binary logs

• All changes done on the server (called events), in the order they were executed.
• Can be inspected easily with the command mysqlbinlog
• Configurable format: Statement, Row or Mixed
• Needed for replication and point in time recovery
• Have a purge (EXPIRE_LOGS_DAYS) and rotation (MAX_BINLOG_SIZE) policy

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Datatypes

More data types, more design choices:
• 9 numeric. Oracle only has one
• INT is 4 bytes, TINYINT 1 byte
• UNSIGNED: double possible values for autoincrements

•DATE (3 bytes), DATETIME (8 bytes) and TIMESTAMP (4 bytes)

Choosing a data type has more impact on the space used
• int(N) – similar to Oracle, does not affect bytes used to store

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Internal components

Data dictionary
• information_schema: metadata about objects
• performance_schema: (5.5.3) dynamic metrics about server usage (as v$ views)

mysql> SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES
-> WHERE TABLE_SCHEMA = 'performance_schema';
+----------------------------------------------+
| TABLE_NAME |
+----------------------------------------------+
| cond_instances |
| events_waits_current |
| events_waits_history |
| events_waits_history_long |
| events_waits_summary_by_instance |
| events_waits_summary_by_thread_by_event_name |
| events_waits_summary_global_by_event_name |
...

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MySQL architecture
Server variables
•Similar to Oracle initialization parameters, change functionality
•Some can be changed dynamically
•Can be persistent changed with startup options or parameter file
•Global/session scope. Global do not affect session who changed it.

mysql root@localhost.information_schema>show variables like 'query%' limit 4;
+------------------------------+---------+
| Variable_name | Value |
+------------------------------+---------+
| query_alloc_block_size | 8192 |
| query_cache_limit | 1048576 |
| query_cache_min_res_unit | 4096 |
| query_cache_size | 0 |
+------------------------------+---------+
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MySQL architecture

Status variables

•Dynamic counters about server activity

mysql root@localhost.information_schema>show status like 'qc%';
+-------------------------+-------+
+-------------------------+-------+
| Qcache_free_blocks | 0 |
| Qcache_free_memory | 0 |
| Qcache_hits | 0 |
| Qcache_inserts | 0 |
| Qcache_lowmem_prunes | 0 |
| Qcache_not_cached | 0 |
| Qcache_queries_in_cache | 0 |
+-------------------------+-------+

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Log Files

Slow query log: can be enabled to record log running queries
long_query_time=N (0 to 10)

General log: can be enabled to record all server activity.
general_log = 'ON'

Error log: start, stop and error messages.
file hostname.err by default
can be changed with log_error=file.log in my.cnf

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Security

Uses standard GRANT/REVOKE commands

Privileges per host/user/database/table/column
grant select on employees.* to you@'desktop' identified by pwd;

Data stored on mysql database: user/db/*_priv tables

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Locking and transactions

Lock handling: specific of the storage engine
InnoDB – row level
MyISAM – table level

Transactions?
• autocommit enabled by default outside transactions
• default tx_isolation is REPEATABLE-READ
• READ_COMMITED does not work with binlog mode STATEMENT

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Locking and transactions

What happens if the server crashes?
• InnoDB has auto recovery (using ib_logfiles)
• MyISAM does not, need manual intervention (myisamchk, repair table)

Some parameters needs to be adjusted if using InnoDB and replication:
• InnoDB_flush_log_at_trx_commit
• sync_binlog
• innodb_support_xa

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AGENDA


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2 - Comparison with Oracle
architecture

Which database flavor?
• Standard? Enterprise? Exadata? Big data appliance?
• There are different implementation decisions in every detail
• Initially created for different purposes

Focus on Standard Edition, some picks:
• Processes handling
• Optimizer features
• Locking
• Memory management

Pick one Oracle functionality, look for that in MySQL.

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SQL

Some SQL differences:
•No need for dual. Select without FROM clause works.
•Dual exists just for compatibility
•No sequences. autoincrement clause at column definition
•last_insert_id() can show the autoincrement value of last insert
•procedures, but no packages and user defined types
•multi-record insert
•insert delayed
•select into outfile / load data file
•drop table if exists
•partial indexes (column(N)) looks like function based index, but they do not exists

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SQL

Case insensitive char comparison

mysql root@localhost.employees>select * from employees
where first_name='JAANA' limit 3;
+--------+------------+------------+-----------------+--------+------------+
| emp_no | birth_date | first_name | last_name | gender | hire_date |
+--------+------------+------------+-----------------+--------+------------+
| 52681 | 1956-03-28 | Jaana | Besselaar | M | 1986-09-26 |
| 53990 | 1960-05-26 | Jaana | Cunliffe | M | 1995-07-09 |
| 54450 | 1954-02-24 | Jaana | Ranon | F | 1988-08-23 |
+--------+------------+------------+-----------------+--------+------------+
8 rows in set (0.01 sec)

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SQL
Silent conversions
mysql root@localhost.employees>create table pru (name varchar(10));
Query OK, 0 rows affected (0.19 sec)

mysql root@localhost.employees>insert into pru values ('Jhon'),('Lindenbaumgreen');
Query OK, 2 rows affected, 1 warning (0.16 sec)
Records: 2 Duplicates: 0 Warnings: 1

mysql root@localhost.employees>show warnings;
+---------+------+-------------------------------------------+
| Level | Code | Message |
+---------+------+-------------------------------------------+
| Warning | 1265 | Data truncated for column 'name' at row 2 |
+---------+------+-------------------------------------------+
1 row in set (0.00 sec)

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SQL
mysql root@localhost.employees>select * from pru;
+------------+
| name |
+------------+
| Jhon |
| Lindenbaum |
+------------+
2 rows in set (0.00 sec)

with SQL_MODE this can be changed:

Mysql> set SQL_MODE=strict_all_tables;

Mysql> insert into pru values ('Jhon'),('Lindenbaumgreen');
ERROR 1406 (22001): Data too long for column 'name' at row 2

NOTE: this works because SET uses SESSION scope by default

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SQL
Many other behaviors can be changed to something Oracle-like:

• SQL_MODE=ORACLE
Equivalent to PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE, NO_KEY_OPTIONS,
NO_TABLE_OPTIONS, NO_FIELD_OPTIONS, NO_AUTO_CREATE_USER.

• SQL_MODE=TRADITIONAL
Equivalent to STRICT_TRANS_TABLES, STRICT_ALL_TABLES, NO_ZERO_IN_DATE,
NO_ZERO_DATE, ERROR_FOR_DIVISION_BY_ZERO, NO_AUTO_CREATE_USER,
and NO_ENGINE_SUBSTITUTION.

• Warning: changing SQL_MODE can hurt tools that expect classic behavior

• Great reference for going deeper on this:
"MySQL Idiosyncrasies that BITE" by Ronald Bradford.

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MySQL Tools

Console
– mysql
– mysqladmin
– mysqldump
– InnoDB Hot Backup: licensed

– Third parties
Percona Toolkit (former maatkit): many useful script utilities
OpenArk: more
Percona XtraBackup: OpenSource non locking transactional backup

– http://forge.mysql.com/tools/

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MySQL Tools

GUI tools

• MySQL Workbench
• Data modeling, SQL development, database management, forward and
reverse engineering, change management.
• Merge and improvement of old tools from MySQL AB.
• Community edition under GPL

• MySQL Enterprise Monitor
• Real time alerting and monitoring solution
• With support contract

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AGENDA


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3 - Installation and Upgrade

• Fresh install:
rpm -Ivh mysql-server

• Customization?
•defaults are for a single installation, single instance per server.
/var/lib/mysql
/etc/my.cnf
/var/log/mysql/mysqld.log
...
• We can create and use our own custom deploy, just to not miss OFA:
/u01?
/u02/mysql/data

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3 - Installation

Default installation
•no root user password. Should be used mysql_secure_installation

Autocommit is enabled. If we want to change it:
mysql root@localhost.employees>set autocommit=off;

mysql root@localhost.employees>show variables like '%autocommit%';
+---------------+-------+
+---------------+-------+
| autocommit | OFF |
+---------------+-------+

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3 - Installation
Do not forget about GLOBAL/SESSION variables:
mysql root@localhost.employees>show global variables like 'autocommit%';
+---------------+-------+
+---------------+-------+
| autocommit | ON |
+---------------+-------+

mysql root@localhost.employees>set global autocommit=off;

mysql root@localhost.employees>show global variables like 'autocommit%';
+---------------+-------+
+---------------+-------+
| autocommit | OFF |
+---------------+-------+
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3 - Installation

Also, variables are not persistent when changed with SET:

oraculo:/var/lib/mysql # service mysql restart
Restarting service MySQL
Shutting down service MySQL done
Starting service MySQL done

mysql root@localhost.(none)>show global variables like '%autocommit%';
+---------------+-------+
+---------------+-------+
| autocommit | ON |
+---------------+-------+

=> It needs to be changed through startup options, in my.cnf file

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3 - Upgrade

Just run rpm -Uvh?

• First on development environments

• Review changes in the new version, looking for:
• new reserved words that could be in use by our existing tables
• parameters in use deprecated/renamed
• data conversion needed for some of our columns?
• known issues

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3 - Upgrade

Effect of upgrading binaries with RPM -Uvh (minor version)
oraculo:~ # service mysql start
Will update MySQL now, if you encounter any problems, please read following file:
/usr/share/doc/packages/mysql-community-server/README.SuSE
Log files inconsistency, please merge following files manually:
/var/log/mysql/mysqld.log
/var/lib/mysql/mysqld.log
Running protected MySQL...
Upgrading MySQL...
Looking for 'mysql' as: /usr/bin/mysql
Looking for 'mysqlcheck' as: /usr/bin/mysqlcheck
Running 'mysqlcheck' with connection arguments: '--port=3306' '--socket=/var/run/my
Running 'mysqlcheck' with connection arguments: '--port=3306' '--socket=/var/run/my
SUELDOS.PARAMETROS_REPORTES OK
...
Running 'mysql_fix_privilege_tables'...
OK
Starting service MySQL done

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3 - Upgrade

Version after the upgrade:

oraculo:~ # mysql --version
mysql Ver 14.14 Distrib 5.5.21, for Linux (x86_64) using readline 6.1

Worked without issues during last versions (on OpenSUSE 11.4)

5.5.18-73.1
5.5.18-74.1
5.5.20-75.1
5.5.20-78
5.5.20-80.1
5.5.21-81.1

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AGENDA


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4 - MySQL Security & auditing

• Privilege ALL includes SUPER, which allows to administer the MySQL
server. Follow least needed principle, and also avoid using %:
GRANT SELECT (col1), INSERT (col1,col2) ON employees.employee TO
'you'@'desk';
GRANT select on employees.* to you@'%' identified by pwd;
GRANT select on *.* to you@'%';
GRANT ALL on *.* to you@'%';

• Each user/host combination defines a unique user

• Vanilla is not possible to block connections to specific users
• Log analysis to have proper auditing in place?
• heavily used servers should use replica, TCP or OS mechanisms.
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4 - MySQL Security & auditing

Auditing

• No built in functionality
• Can be implemented with triggers, sames as with Oracle
• TIMESTAMP datatype has automatic updating and initialization, no
triggers needed

col_name TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP

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AGENDA


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5 - Performance Management

NOs:
• way of modify/cheat optimizer statistics as in Oracle
• historical repository like AWR – Enterprise Monitor with support contract
• limits on server CPU/IO usages
• ability to rewrite queries on the fly

Can:
• configure many internal memory areas and number of client threads
• use hints to force index usage
• use external home made solution for query rewrite

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• classical unix tools outside the database
vmstat / oprofile / strace / top
gdb – poor man's profiler

• inside database
• mytop / innotop utilities
• explain / explain extended
• before MySQL 5.6.3, subqueries in the FROM clause are executed
• status variables
• com_*, innodb_*, connections
• information_schema
• show engine status / processlist
• profiles

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mysql >set profiling=1; mysql >show profile for query 1;
Query OK, 0 rows affected (0.00 sec) +----------------------+----------+
| Status | Duration |
mysql >select count(1) From employees; +----------------------+----------+
+----------+ | starting | 0.000142 |
| count(1) | | checking permissions | 0.000017 |
+----------+ | Opening tables | 0.140542 |
| 10000 | | System lock | 0.000039 |
+----------+ | init | 0.000022 |
1 row in set (0.21 sec) | optimizing | 0.000008 |
| statistics | 0.000011 |
mysql >show profiles; | preparing | 0.000009 |
+----------+------------+--------------------------------+ | executing | 0.000005 |
| Query_ID | Duration | Query | | Sending data | 0.075795 |
+----------+------------+--------------------------------+ | end | 0.000018 |
| 1 | 0.21665250 | select count(1) From employees | | query end | 0.000007 |
+----------+------------+--------------------------------+ | closing tables | 0.000012 |
1 row in set (0.00 sec) | freeing items | 0.000020 |
| logging slow query | 0.000003 |
| cleaning up | 0.000005 |

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AGENDA


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6 - Backup & Recovery

mysqldump – logical backup, engine independent
full, database or table
locking based on storage engine used

XtraBackup – open-source hot backup / non-locking tool from Percona

Hotbackup with InnoDB
hotbackup: mysqldump --single-transaction --master-data
XtraBackup: innobackupex /data/backups
Needs an extra step to prepare prior to use in recovery
www.percona.com/doc/percona-xtrabackup/

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AGENDA


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7 - Designing for High Availability

Replication – built in:
• Transfer and apply binary log from master to slaves.
• Simple to setup.
• Flexible to create cascade configurations.
• Can be partial, filtering by DB, tables, and combined.
• Asynchronous. Semi-sync in 5.5.
• Easy to break. Needs periodical consistency checks.
• No conflict resolution. Needs manual intervention when detected.
• Not automated failover for HA.
• Apply single threaded until 5.6.
• Can be configured as circular, but it needs application level coding to avoid
inconsistencies.

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7 - Designing for High Availability

MySQL Cluster
• Different distribution and binaries from MySQL 5.5
• Shared nothing architecture: Data nodes, SQL nodes and Manager.
• Data is stored redundant among Data nodes
• Online operations: backup, upgrade, node provisioning
• Memory usage tied to data handled and #nodes in the cluster
• 7.2 recent in production with many improvements

Other solutions
• SAN/DRBD: Protection from server failures
• Pacemaker: Cluster resource manager. Automation of HA among servers.
• Galera: Synchronous replication as server plugin. Community and Enterprise.
• Tungsten: MultiMaster replication at application level. Community and Enterprise.

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Last remarks

• MySQL addresses the same problems as Oracle Database.
• Do not look for same functionality, but ACID and performance.
• Some specific task can be easier (example: Partitioning).
• Need to develop custom scripts for admin tasks, using standard OS tools.
• Big community of users.
• Being FOSS software, source code is available. This allows to overcome lack of
specialized tools for specific issues, and depending on your skills you can fix your
own problems, and benefit the community.
• Many improvements by other companies (as Percona and Facebook).

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Questions?

nelson.calero@gmail.com

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Tip: Better command line prompt

Command line could be tuned similar to sqlplus with glogin script?
oracle@oraculo:~> sqlplus / as sysdba

SQL*Plus: Release 11.2.0.2.0 Production on Tue Feb 28 22:09:00 2012
Copyright (c) 1982, 2011, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Express Edition Release 11.2.0.2.0 - 64bit Production

22:09:01 SYS@XE>

oracle@oraculo:~> tail $ORACLE_HOME/sqlplus/admin/glogin.sql
set pagesize 200
set linesize 120
SET TIME ON TIMING ON
SET SQLPROMPT '&_user@&_connect_identifier>'

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Tip: Better command line prompt
Add PROMPT parameter to /etc/my.cnf
[mysql]
no-auto-rehash
prompt=mysql u@h.d>

oraculo:~ # mysql
Welcome to the MySQL monitor. Commands end with ; or g.
Your MySQL connection id is 7
Server version: 5.5.21-log Source distribution
Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective owners.
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql root@localhost.(none)>use information_schema
Database changed
mysql root@localhost.information_schema>

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Collaborate 2012 - Administering MySQL for Oracle DBAs

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