14 Copyright © 2005, Oracle. All rights reserved. System Management Tasks and Techniques.

14Copyright © 2005, Oracle. All rights reserved.

System Management Tasks and Techniques

14-2 Copyright © 2005, Oracle. All rights reserved.

Objectives

After completing this lesson, you should be able to do the following:

• Demonstrate table and partition compression techniques

• Implement resumable sessions in your data warehouse

• Implement an effective backup and restore strategy for your data warehouse

• Plan a security strategy for a data warehouse


Are There Execution Problems?

• Use V$PQ_TQSTAT to find out if there is data distribution skew or bad object statistics:– Contains traffic statistics between slaves at table

queue level– Valid only when queried from the parallel session

• Check I/O and CPU bound at the operating system level and decide on the parallelism

• Use the Automatic Workload Repository to examine useful statistics


Performance Monitoring and Tuning

• Statistics gathering and monitoring activities are mainly automatic.

• Administer and display the output of the gathering and tuning tools with Enterprise Manager:– Automatic Workload Repository– Automatic Database Diagnostic Monitor– SQL Access Advisor– End to End Application Tracing


Statistics Collection

• The STATISTICS_LEVEL initialization parameter controls major statistics collection in the database.

• STATISTICS_LEVEL can have one of three values:– When set to BASIC, no advisories or statistics are

collected.– TYPICAL is the default value and ensures

collection for all major statistics.– ALL includes all items collected with

TYPICAL plus operating system androw source execution data.


End to End Application Tracing

End to End Application Tracing:

• Simplifies the process of diagnosing performance problems in multitier environments

• Helps to identify the source of an excessive workload

• Uses a client identifier to uniquely trace a specific end client through all tiers

• Allows you to identify what a user’s session is doing at the database level


End to End Application Tracing Using EM

EM Database Control interface:


Compression

• Table compression is optimized for relational data.

• There is virtually no negative impact on the performance of queries against compressed data.

• There can be a significant positive impact on queries accessing large amounts of data.

• The data is compressed by eliminating duplicate values in a database block.

• All database features and functions that work on regular blocks also work on compressed blocks.


What Can Be Compressed?

• Objects that can be compressed include:– Tables – Partitions– Materialized views– B-tree indexes

• Compression works for all data types except:– Variants of large objects (LOBs) – Data types derived from LOBs, such as VARRAYs

stored out of line or XML data type stored in a character large object (CLOB)

• Tables that are frequently updated should not be compressed.


Compression: Examples

• Simple compressed partitioned table:

• Partitioned table with one compressed partition:

CREATE TABLE sales_rangesalesman_id NUMBER(5),salesman_nameVARCHAR2(30),sales_amount NUMBER(10),sales_date DATE)COMPRESSPARTITION BY RANGE(sales_date)...

CREATE TABLE sales_list(salesman_id NUMBER(5),salesman_name VARCHAR2(30),sales_state VARCHAR2(20),sales_amount NUMBER(10))PARTITION BY LIST(sales_state)(PARTITION sales_west VALUES('California', 'Hawaii') COMPRESS,PARTITION sales_east VALUES('New York', 'Virginia', 'Florida'),...


Maximizing Compression Ratios

• Load data ordered (sorted) to maximize the duplication of values within a database block.

• If external tables are used for loading, add an ORDER BY clause to the SELECT statement.

• Use larger block sizes.


Resumable Sessions

• Resumable statements enable large database operations to be suspended and resumed.

• Space-limit errors can be corrected, allowing the hung session to resume.

• Issue ALTER SESSION ENABLE RESUMABLE before initiating a long-running operation:

– TIMEOUT specifies the time window for intervention.– NAME specifies the name of the resumable session.

ALTER SESSION ENABLE RESUMABLE TIMEOUT 600 NAME 'resumable_session_name';


Data Warehouse Backup and Recovery

Why should a data warehouse backup and recovery strategy not be just like that of an OLTP database?• A data warehouse is typically much larger than an

operational system.• A data warehouse often has lower availability

requirements than an OLTP system.• Data warehouse updates are

often reproducible from sources other than database logs.

• Data warehouses containhistorical data and often, large portions of the older data are static.


Recovery Time Objective (RTO)

An RTO is the number of hours in which you want to be able to recover your data. To formulate an RTO:

• Understand your recovery readiness, risk areas, and the business costs of unavailable data.

• Transform the recovery requirements into backup and recovery strategies.

• Deploy and integrate the solution into your environment to back up and recover your data.

• Test your recovery plans at regular intervals.– Refine it as your data, IT infrastructure, and

business processes change.


Recovery Point Objective (RPO)

Automated recovery

procedures

Manual recovery

procedures

No backup of data

Restore backup

Data reinserted

via ETL

RPOBackups

run at scheduled intervals.

RTO #1Critical data is available, database is

open.

RTO #2Remainder of data is inserted.

0-nn hours +nn hours +nnn hours

Normal operations

Normal operations


More Backup and Recovery Considerations

• Hardware is the limiting factor to fast backup and recovery.– More data means a longer backup window.

• RMAN can fully utilize, in parallel, all available tape devices.

• Consider breaking the database backup over a number of days.

• RMAN backs up all database files that have not been backed up in the last 24 hours.

• The backup job is limited to 4 hours.

RMAN> BACKUP DATABASE NOT BACKED UP SINCE \ 'sysdate – 1' PARTIAL DURATION 4:00 MINIMIZE TIME;


Backup and Recovery Tools

• Recovery Manager reduces the administration work associated with your backup strategy.

• Enterprise Manager enables backup and recovery to be done by a point-and-click method.

• Data Pump provides high-speed, parallel, bulk and metadata movement of database contents.

• User-managed backups are done using operating system–specific utilities.


Backup and Recovery:Best Practices

• Use ARCHIVELOG mode.

• Use RMAN.

• Leverage read-only tablespaces.

• Plan for nologging operations in your backup and recovery strategy.

• Not all tablespaces in a data warehouse are equally significant from a backup and recovery perspective.


NOLOGGING Backup and Recovery Strategies

Extract, transform, load (ETL):

• Uses several Oracle tools and a combination of methods to reload data– Transportable tablespaces, SQL*Loader, Data

Pump, external tables

Incremental backups:

• Are a more automated backup and recovery strategy in the presence of nologging operations

• Provide the capability to back up only the changed blocks since the previous backup

• Are faster when using the block change tracking feature


Employing Incremental Backups

• Incremental backups of data files capture data changes on a block-by-block basis.

• Speed up backups by using block change tracking– The database tracks the physical location of all

database changes.– RMAN automatically uses the change tracking file

to determine which blocks need to be read.– Sizing the block change tracking file:

• Best practice: Use block change tracking and make an incremental backup after nologging direct load operations.

((threads * 2) + number_of_old_backups) * (database_size_in_bytes)--------------------------------------------------------------------------------------------------

250000


Data Warehouse Security

The consolidated model provides several benefits for data warehouse security:

• Consistent security model

• Central, expert management

• Fewer points of attack

• Simpler security maintenance


Layered Security Model

• Provide multiple security layers so that failure of a single layer does not compromise critical data.

• The security layers available in Oracle Database 10g include:– Role-based access control– Row-level security employing

Virtual Private Database and Oracle Label Security

– Auditing the database– Encryption


Transparent Data Encryption

• Transparent Data Encryption (TDE) is a component of Oracle Advanced Security.

• TDE allows you to encrypt selected column data without having to manage the encryption key.

• Encrypt sensitive data such as credit card numbers before it is stored in the database.

• Oracle Advanced Security protects data by using industry-standard encryption methods:– AES– Triple DES


Implementing TDE

1. As SYSDBA, create the encrypted wallet file and set the initial password:

2. Create the table:

3. Verify encryption:

ALTER SYSTEM SET ENCRYPTION KEY IDENTIFIED BY "secret_passwd";

create table SH.CUST_SS_INFO(first_name varchar2(11), last_name varchar2(10),ss_num varchar2(20) ENCRYPT NO SALT);

SQL> select * from DBA_ENCRYPTED_COLUMNS;OWNER TABLE_NAME COLUMN_NAME ENCRYPTION_ALG SAL----- ------------- ----------- ---------------- ---SH CUST_SS_INFO ss_num AES 192 bits key NO


Summary

In this lesson, you should have learned how to:

• Demonstrate table and partition compression techniques

• Implement resumable sessions in your data warehouse

• Implement an effective backup and restore strategy for your data warehouse

• Plan a security strategy for a data warehouse


Practice 14: Overview

This practice covers the following topics:

• Implementing table compression and investigating the resultant compression ratios

• Using resumable sessions

• Implementing Transparent Data Encryption

14 Copyright © 2005, Oracle. All rights reserved. System Management Tasks and Techniques.

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