这是转摘得一篇文章。

The primary goal of RMAN tuning is to create an adequate flow of data between disk and storage device. Tuning RMAN backup and restore operations involves the following tasks discussed in this chapter:

• Tuning Recovery Manager: Overview

• RMAN Tuning Concepts

• Improving RMAN Backup Performance

Oracle provides several indexing schemes, which provide complementary performance functionality:

This chapter explains why statistics are important for the cost-based optimizer and how to gather and use statistics.

The chapter contains the following sections:

• Understanding Statistics

• Generating Statistics

• Using Statistics

• Using Histograms

此系转抄： 查看全文

热备份的时候，只读表空间不需要执行begin backup.直接使用操作系统命令备份就可以。一旦表空间变为read-only,Oracle就不会再写对应的数据文件。

　　如下 对只读表空间执行begin backup,提示错误信息

alter tablespace mgn_readonly_Test read only;

SQL> alter tablespace mgn_readonly_Test begin backup;

alter tablespace mgn_readonly_Test begin backup

*

ERROR at line 1:

ORA-01642: begin backup not needed for read only tablespace 'MGN_READONLY_TEST'

　　只读表空间恢复

　　当对数据库进行完全恢复的时候，只需要将READONLY表空间数据文件拷贝回去即可。

以下是常用脚本，会陆续加入许多。

这篇文章是对oracle文档中Using LogMiner to Analyze Redo Log Files的译注。

Oracle LogMiner, which is part of Oracle Database, enables you to query online and archived redo log files through a SQL interface. Redo log files contain information about the history of activity （数据库活动的历史信息）on a database.

（通过sql interface查询online 和 archive redo log files）

位图索引的使用：

1.Bitmap indexing benefits data warehousing applications
2.Bitmap indexes are not suitable for OLTP applications with large numbers of concurrent transactions modifying the data.
3.Bitmap indexes are also not suitable for columns that are primarily queried with less than or greater than comparisons.
4.Bitmapped indexes are only useful with equality queries, especially in combination with AND, OR, and NOT operators.
5.The advantages of using bitmap indexes are greatest for low cardinality columns
6.B-tree indexes are most effective for high-cardinality data
7.In ad hoc queries and similar situations, bitmap indexes can dramatically improve query performance. AND and OR conditions in the WHERE clause of a query can be quickly resolved by performing the corresponding Boolean operations directly on the bitmaps before converting the resulting bitmap to rowids.
8.bitmap indexes must be local to the partitioned table
9.Bitmap indexes can include rows that have NULL values

Purpose

The logging_clause lets you specify whether creation of a database object will be logged in the redo log file (LOGGING) or not (NOLOGGING).

(制定创建数据库对象时是否在redo log file中记录日志)

You can specify the logging_clause in the following statements:

• CREATE TABLE and ALTER TABLE: for logging of the table, a table partition, a LOB segment, or the overflow segment of an index-organized table (see CREATE TABLE and ALTER TABLE).

• CREATE INDEX and ALTER INDEX: for logging of the index or an index partition (see CREATE INDEX and ALTER INDEX).

• CREATE MATERIALIZED VIEW and ALTER MATERIALIZED VIEW: for logging of the materialized view, one of its partitions, or a LOB segment (see CREATE MATERIALIZED VIEW and ALTER MATERIALIZED VIEW).

• CREATE MATERIALIZED VIEW LOG and ALTER MATERIALIZED VIEW LOG: for logging of the materialized view log or one of its partitions (see CREATE MATERIALIZED VIEW LOG and ALTER MATERIALIZED VIEW LOG).

• CREATE TABLESPACE and ALTER TABLESPACE: to set or modify the default logging characteristics for all objects created in the tablespace (see CREATE TABLESPACE and ALTER TABLESPACE).（设置或修改在该表空间中创建的对象的defaut logging cgaracteristics,影响在该表空间中创建的所有对象）

You can also specify LOGGING or NOLOGGING for the following operations:

• Rebuilding an index (using CREATE INDEX ... REBUILD)

• Moving a table (using ALTER TABLE ... MOVE)

本文是对文档中Instance Recovery Performance Tuning的译注。

This section describes instance recovery, and how Oracle's Fast-Start Fault Recovery improves availability in the event of a crash or instance failure. It also offers guidelines for tuning the time required to perform crash and instance recovery.

This section contains the following topics:

· Understanding Instance Recovery

· Checkpointing and Cache Recovery

· Configuring the Duration of Cache Recovery: FAST_START_MTTR_TARGET

Tuning FAST_START_MTTR_TARGET and Using MTTR Advisor

Shared memory can be dumped to trace file using
$ sqlplus /nolog
SQL> CONNECT SYS/<password> AS SYSDBA
Connected
SQL> ORADEBUG SETMYPID
Statement processed
SQL> ORADEBUG IPC
Information written to trace file
SQL> ORADEBUG TRACEFILE_NAME
/var/opt/oracle/admin/LX092001/udump/lx092001_ora_9824.trc

Granules can be dumped using
ALTER SESSION SET EVENTS‘immediate trace name granulelist level <level>’
Heap Level
Null Granule 255
Home Granule 511
Shared Pool 767
Large Pool 1023
Java Pool 1279
Buffer Cache 1535

Global Area Dumps
ALTER SESSION SET EVENTS‘immediate trace name global_area level <level>’
Heap Level
PGA 1
SGA 2
PGA + SGA 3
UGA 4
PGA + UGA 5
SGA + UGA 6
PGA + SGA + UGA 7

Heap Dumps
ALTER SESSION SET EVENTS‘immediate trace name heapdump level <level>’;
Heap Summary Detail
PGA 1 1025
SGA 2 2050
UGA 4 4100
CGA – Current Call 8 8200
CGA – User Call 16 16400
LGA – Large Pool 32 32800

Subheap Dumps
In Oracle 9.0.1 and below to dump a subheap, first obtain the address of the subheap and convert to decimal
0x56b95c0c = 1454988300
For a summary dump use
ALTER SESSION SET EVENTS ‘immediate trace name heapdump_addr level 1454988300’;
For a detailed dump add 1 to the address e.g.
ALTER SESSION SET EVENTS ‘immediate trace name heapdump_addr level 1454988301’;
In Oracle 9.2 and above to dump the subheap summary use
ALTER SESSION SET EVENTS ‘immediate trace name heapdump_addr level 1, addr 0x56b95c0c’;
For a detailed dump use
ALTER SESSION SET EVENTS ‘immediate trace name heapdump_addr level 2, addr 0x56b95c0c’;

(Identifying, measuring, and resolving harmful latch contention)

Latest version available at http://www.orapub.com

2 Craig A. Shallahamer

©OraPub, Inc.

This page has been intentionally left blank.

Conquering Oracle Latch Contention 3

©OraPub, Inc.

Table of Contents

TABLE OF CONTENTS ............................................................................................................... 3

INTRODUCTION......................................................................................................................... 4

HOW TO LEAN ABOUT ORACLE LATCHING................................................................................... 4

THE PROCESS EXPLAINED...................................................................................................... 5

UNDERSTANDING THE GENERAL LATCHING ALGORITHM........................................ 6

TYPES OF ORACLE LOCKS ............................................................................................................. 6

THE ORACLE LATCH ..................................................................................................................... 7

THE GENERAL ORACLE LATCHING ALGORITHM........................................................................... 7

HOW MULTIPLE LATCHES ARE IMPLEMENTED ............................................................................. 8

HOW TIME IS RECORDED............................................................................................................... 9

HOW TO DETECT HARMFUL LATCH CONTENTION..................................................... 10

RESOLVING HARMFUL LATCH CONTENTION ............................................................... 12

CONCLUSION............................................................................................................................ 13

ABOUT THE AUTHOR.............................................................................................................. 13

REFERENCE ............................................................................................................................... 14

4 Craig A. Shallahamer

©OraPub, Inc.

Tanel Peter

independent consultant

http://integrid.info

Oracle OpenWorld 2005

Introduction & About

• Name: Tanel P鮠er

• Oracle experience: 8 years

• Occupation: independent consultant

• Company: integrid.info

• Member of Oaktable Network

• Oracle Certified Master DBA

本方案主要保护数据库系统在发生system failure or other disaster（如：power failures, or from physical disasters such as fire, floods, or earthquakes）时，快速的恢复系统，减少系统的宕机时间，减少对业务的影响，尽量做到数据不丢失。
容灾系统采用oracle 数据库提供的standby database,standby dayabase 工作在managed standby database方式，并且备用数据库放置在与主数据库相隔一定距离的备用机房，这样即使在主机房发生自然灾害等，也能够很容易的快速的实现灾难恢复。下面就我院standby database的实现作具体的说明： 查看全文