This document summarizes the results of comparing standard Vacuum and Vacuum Full operations in PostgreSQL. Standard Vacuum deletes just deleted tuple identifiers, while Vacuum Full rewrites the entire table. The summary describes how inserting, deleting, and vacuuming data affects the table size and contents as seen in the data files.
This technical report discusses configuration of the Performance Schema in MySQL 5.6. It describes configuration tables for setting monitoring targets, consumers, instruments, and objects. It shows commands for checking default settings and updating configurations. Benchmarks with different Performance Schema settings show throughput decreased when instruments were enabled but wait events only configuration had less impact than fully enabling instruments.
This document summarizes the results of comparing standard Vacuum and Vacuum Full operations in PostgreSQL. Standard Vacuum deletes just deleted tuple identifiers, while Vacuum Full rewrites the entire table. The summary describes how inserting, deleting, and vacuuming data affects the table size and contents as seen in the data files.
This technical report discusses configuration of the Performance Schema in MySQL 5.6. It describes configuration tables for setting monitoring targets, consumers, instruments, and objects. It shows commands for checking default settings and updating configurations. Benchmarks with different Performance Schema settings show throughput decreased when instruments were enabled but wait events only configuration had less impact than fully enabling instruments.
데이터베이스 수업도 듣고 선임자가 건네준 모델대로 구현해본 경험이 제법 있더라도, 막상 자신이 책임자가 되어 백지 위에 엔터티 박스와 관계선을 그려야 한다면 막막함이 앞을 가린다. 이전에 본 듯한 패턴을 흉내 내 그림을 그려보지만 수백, 수천의 엔터티 홍수 속에서 제대로 가고 있다는 확신이 서지 않는다.
저자는 이처럼 너무도 거대한 현업의 복잡함에 압도되어 길을 잃고 고생하는 후임들의 안타까운 모습에 직접 멘토가 되어주고자 이 책을 쓰기 시작했다. 내공이 깊어야 연공이 자유롭듯, 그 본질을 꿰고 있다면 어떤 업무가 주어지든 막힘없이 헤쳐나갈 수 있다. 짧은 호흡으로 경쾌하게 풀어낸 이야기들을 통해 따스한 온기가 묻어 있는 저자의 노하우를 내 것으로 만들자.
[오픈소스컨설팅]Day #1 MySQL 엔진소개, 튜닝, 백업 및 복구, 업그레이드방법Ji-Woong Choi
MySQL 소개
간략한 소개
version history
MySQL 사용처
제품 군 변화
시장 변화
MySQL 구성
MySQL 클라이언트 / 서버 개념
클라이언트 프로그램
MySQL 설치
MySQL 버전
MySQL 설치
MySQL 환경 설정
환경설정, 변수 설정
MySQL 스토리지 엔진 소개
MySQL tuning 소개 및 방법
데이터 백업/복구 방법
백업
복구
MySQL Upgrade
This document discusses transaction slot before-image chaining in Oracle databases. It begins with questions about cleanout, undo storage, and commit SCNs. It then describes the architecture of before-image chaining, where commit SCNs and other metadata are stored in undo blocks and transaction control blocks to link a transaction's multiple before-images together. Diagrams show how before-images are chained across multiple undo blocks using these references.
The document outlines the agenda for the 8th demand seminar held by EXEM, including presentations on PostgreSQL Vacuum and MySQL locks. The PostgreSQL presentation covers the details of Vacuum including its behavior during updates, deletes, and different Vacuum commands. The MySQL presentation covers different types of locks in MySQL including global read locks, table locks, and string locks.
This document discusses debugging PHP applications with XDebug. It introduces XDebug and its features like profiling and tracing code. It explains how to install and configure XDebug, including settings in php.ini. It also describes using XDebug with IDEs like PHPStorm and web browsers through extensions. The document provides an example of using XDebug to time code execution and references for further information.
1. The document describes how Oracle allocates CU blocks and CR blocks in the buffer cache when updating column values from A to I through consecutive commits.
2. It shows the expected outcome of 6 CR blocks being allocated for the 6 updates before a new CU block is needed.
3. Using a tool to view the internal Oracle buffer cache, it demonstrates this expected behavior, showing the CR blocks and CU blocks allocated for updates from A to I.
The document describes the Oracle undo segment and how it tracks changes to data in transactions.
1) It shows the initial state when a value of "A" is entered into a table column.
2) It then shows an update transaction that changes the value from "A" to "B", with the undo segment recording the before image of "A".
3) A second update transaction is shown, changing the value from "B" to "C", with the undo segment recording the before images of "B" and "A".
발표영상 다시보기: https://kr-resources.awscloud.com/data-databases-and-analytics/%EC%98%A4%EB%9D%BC%ED%81%B4-db%EB%A5%BC-aws-%EB%8D%B0%EC%9D%B4%ED%84%B0%EB%B2%A0%EC%9D%B4%EC%8A%A4%EB%A1%9C-%EB%A7%88%EC%9D%B4%EA%B7%B8%EB%A0%88%EC%9D%B4%EC%85%98-%ED%95%98%EA%B8%B0-%EC%9C%A4%EA%B8%B0%EC%9B%90-aws-database-modernization-day-%EC%98%A8%EB%9D%BC%EC%9D%B8-2
온프레미스 Oracle DB를 AWS Database Migration Service와 Schema Conversion Tool을 사용하여 Migration하는 방법을 소개합니다. Migration시 Service Downtime을 최소화 하고, Migration 속도를 향상 시킬 수 있는 방법을 알아봅니다.
The document provides information about Amazon Aurora including:
- An overview of Amazon Aurora describing its high performance, scalability, availability and security features compared to other databases.
- Details on Amazon Aurora's architecture which uses a multi-tenant storage layer and integrates with other AWS services for backups, replication and high availability across Availability Zones.
- Descriptions of new Aurora capabilities like Multi-Master which allows applications to read and write to multiple database instances for increased availability without downtime.
1. The document describes how Oracle allocates CU blocks and CR blocks in the buffer cache when updating column values from A to I through consecutive commits.
2. It shows the expected outcome of 6 CR blocks being allocated for the 6 updates before a new CU block is needed.
3. An analysis using ODI Analyzer on an Oracle database shows this expected behavior occurring, with CR blocks 1-6 being allocated and reused for each update before a new CU block is created on the 7th update.
[ODI] chapter3 What is Max CR DBA(Max length)? EXEM
The document discusses how Oracle's buffer cache allocates consistent read (CR) blocks and current (CU) blocks when updating a single column value in a table multiple times with commits. It finds that with the parameter _db_block_max_cr_dba set to 6, Oracle allocates a new CU block for each update while reusing the first 6 CR blocks, allocating a new one for the 7th update. Screenshots from an internal tool show the state of blocks in the buffer cache after each update.
[ODI] chapter2 what is "undo record chaining"?EXEM
- Undo record chaining allows Oracle to rollback multiple transactions by linking undo records together in a chain.
- When an update is made, an undo record is generated and added to the undo block. A new record contains the before image of the update.
- Undo records for a transaction are chained together by transaction ID and sequence number. This allows Oracle to efficiently rollback a whole transaction by traversing the undo record chain.
[ODI] chapter1 When Update statement is executed, How does oracle undo work?EXEM
When an update statement is executed in Oracle, the undo mechanism works as follows:
1. Oracle generates a new change undo (CU) block in the buffer cache to track the before image of the updated row.
2. The original data block is copied to the new CU block, and the original block is marked as a change redo (CR) block.
3. Oracle allocates memory and assigns a transaction ID (XID) to the transaction in the V$TRANSACTION view, tracking the undo information for the update.
엑셈 편집부, 『그림으로 명쾌하게 풀어쓴 Practical OWI in Oracle 10g』, 엑셈(2007)
실제 Practical OWI 세미나에서 사용됐던 다양하고 상세한 그림을 그대로 사용하면서 시각적인 효과를 높이고, 상세한 설명을 통해 최대한 그림에 대한 이해를 돕도록 했습니다.
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EXEM
- 네이버 블로그: http://blog.naver.com/playexem
- Youtube 엑셈 tv: https://www.youtube.com/channel/UC5wKR_-A0eL_Pn_EMzoauJg
- Maxgauge facebook: https://www.facebook.com/yourmaxgauge/
PostgreSQL는 다른 RDBMS와 다르게 vacuum이라는 명령어가 있습니다. 특정 튜플을 update하거나 delete 한다고 해서 해당 영역이 자동으로 재사용되거나 사라지지 않는다. 이렇게 오래된 영역을 정리하여 공간을 반환하는 명령어가 Vacuum이다. ≒ 디스크 조각 모음
Oracle, InnoDB는 rollback segment를 사용하여 MVCC 구현하지만, Postgres에서는 내부페이지를 사용함. 즉 update, delete된 행을 즉시 제거하지 않음. 결국에는 이공간을 VACUUM작업을 통해서 회수해야함.
갱신 · 삭제를 할 경우, FSM을 검색하여 불필요한 공간을 회수합니다.
Oracle, InnoDB는 rollback segment를 사용하여 MVCC 구현하지만, Postgres에서는 내부페이지를 사용함. 즉 update, delete된 행을 즉시 제거하지 않음. 결국에는 이공간을 VACUUM작업을 통해서 회수해야함.
갱신 · 삭제를 할 경우, FSM을 검색하여 불필요한 공간을 회수합니다.
Oracle, InnoDB는 rollback segment를 사용하여 MVCC 구현하지만, Postgres에서는 내부페이지를 사용함. 즉 update, delete된 행을 즉시 제거하지 않음. 결국에는 이공간을 VACUUM작업을 통해서 회수해야함.
갱신 · 삭제를 할 경우, FSM을 검색하여 불필요한 공간을 회수합니다.