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M_14_1.00 Scalability And High Availability with demos and labs.pdf

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    Module 14:

    Scalability and HighAvailability

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    Overview

    Key high availability features available in Oracle andSQL Server

    Key scalability features available in Oracle and SQLServer

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    High Availability

    High availability ensuring database and data areaccessible for the maximum amount of time

    Initialization parameters or configuration options inOracle and SQL Server

    Logical (add, remove, rename columns) and physical(rebuild, move, change storage parameters) structure oftables

    Online index operations

    SQL Server partitioning option

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    Clustering

    Both Oracle and SQL Server offer Active/Passive (single instance)and Active/Active (multi-instance failover clustering) options inclustering. In Oracle, it is called Failsafe and Real ApplicationClusters (RAC); SQL Server refers to it as Failover Clustering

    For Active/Passive clustering, Failsafe and Failover clustering areboth based on Microsoft Cluster Services (MSCS) containing asingle set of non-shared disks

    For Active/Active clustering, Failsafe and Failover clustering utilize amulti-node configuration where each node has its own instanceconnecting to shared disks. However, the database can be openedby only one node at a time

    Oracles RAC can also provide Active/Active clustering in a shared-everything architecture where multiple instances cansimultaneously access data from the same database

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    Standby Database

    Both offer standby database which can be used foravailability and disaster recovery

    In Oracle, Data Guard

    In SQL Server, AlwaysOn, Database Mirroring, and Log Shipping

    Standby databases are updated using archive logs inOracle and transaction logs in SQL Server

    Shipping of logs to a standby server and theirapplication can be controlled to provide scope for

    recovery from user errors in the primarySnapshots of mirrored database in SQL Server andlogical standby database in Oracle can be used for read-only purposes such as reporting, analysis, DSS

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    Database Mirroring

    Software solution for increasing the availability of aspecific database

    Consists of principal server, a mirror server, andoptionally a witness server

    Witness server enables automatic failoverCan operate in either Synchronous or Asynchronousmode

    Use views such as sys.database_mirroring,

    sys.dm_db_mirroring_connections to monitor databasemirroring

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    Demonstration: Database Mirroring

    In this demonstration you will learn to:

    Prepare Database on Instances

    Configure Database Mirroring

    Execute Failovers Between Instances

    Utilize the Mirror for Read-OnlyProcessing with Database Snapshots

    Monitor Activity Between Instances

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    SQL Server 2012 AlwaysOn

    NEW high availability and disaster recovery solutionAchieving required 9s

    Availability Groups on multiple databases

    Multi-subnet clustering supportHardware utilization and performance

    Active secondaries (reporting, backup)

    Reduced planned downtime

    Windows Server Core support

    Rolling upgrade support

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    SQL Server 2012 AlwaysOn Details

    Failover Cluster Instances:

    Flexible failover policy for cluster health detection

    Indirect checkpoints

    Availability Groups:Asynchronous or synchronous modes

    Listeners for fast application failover

    Flexible failover policy

    Automatic page repair against page corruption

    Encryption and compression for security and high

    performance transport

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    SQL Server 2012 AlwaysOn Tools

    T-SQL DDL statementsWizards

    New Availability Group

    Add database to Availability GroupAdd replica to Availability Group

    Failover Availability Group

    AlwaysOn Dashboard for Availability Group health view

    Object Explorer Details for Availability Group info

    PowerShell cmdlets for automation

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    Demonstration: AlwaysOn

    In this demonstration you will learn to:Implement AlwaysOn Availability Groups

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    Replication Objects

    Replication is a specialization of the distributed database conceptwhere copies of an object can be kept in multiple databases

    Unlike clustering and standby databases, replication encouragessharing and distribution of individual objects rather than entiredatabases

    Both Oracle and SQL Server provide multiple types of replicationbased on whether the replicas are read-only or updatable

    Replicas are refreshed in full or updated using discrete transactionseither synchronously (multi-master) or asynchronously (all others)

    Oracle Streams offers replication in three forms:

    Multi-master replication multiple peer-to-peer updatable replicas

    Materialized views each replica has a master site with variouspolicies on updating the replicas

    Hybrids of replication and materialized views

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    Replication Types

    SQL Server offers the following types of replication: Snapshot replication used mostly as read-only copies which are

    completely refreshed periodically

    Transactional replication kept up-to-date with immediate or

    deferred updates from the master site. Copies are used mostly as

    read-only and occasionally updated. Updatable subscribers

    (immediate and queued), and peer-to-peer transactional replication

    support updates at subscribers.

    Merge replication similar to Oracles multi-master replication

    where the autonomous sites are synchronized at regular intervals

    Oracle and SQL Server offer sophisticated algorithms for conflictresolution among updatable replicas

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    Demonstration: Replication

    In this demonstration you will learn to:Define the Roles of Replication

    Define the Publication and Articles

    Implement Peer-to-Peer Replication

    Use the new Configure Peer-to-PeerTopology Tool

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    Scalability

    Scalability is the ability to support very large databases (VLDB)and/or large volume OLTP

    Memory areas in Oracle and SQL Server are dynamically resizedwithout restarting. The process is performed either automatically orby the DBA in Oracle, where it is automatically performed by theDBMS in SQL Server.

    Oracle uses parallel query slaves and SQL Server uses workerthreads to provide interoperation and intra-operation parallelism inthe execution of DML and DDL. Both optimizers are parallel-aware.

    Oracle and SQL Server scale well in the handling of userconnections through the use of shared server processes

    Oracle and SQL Server offer many types and features for speedyaccess to large volumes of data. Examples are many types ofindexes, advanced I/O techniques and caching.

    SQL Server supports NUMA and Hot Add CPU

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    Scalability and HA in Backup and Recovery

    MTTR targets can be set for instance recovery by controlling the

    checkpoint process in Oracle using FAST_START MTTR_TARGET

    and in SQL Server using recovery interval option

    The RMAN features available in SQL Server backup and restore

    utilities are:

    Parallelism in backup and recovery operations Incremental backups

    Multiple granularities in backup and restore to reduce the amount ofrecovery needed

    Point in time recovery

    Choice of backup media and devices

    Duplicating or cloning databases

    Moving of data in logical units of tablespaces using transportable

    tablespaces across multiple platforms in Oracle is found in SQL

    Server through the attach and detach features for databases

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    Review

    We defined high availability and the role it plays inmodern day businesses

    We covered all the important high availability features inOracle and SQL Server. The major ones being failoverclustering, standby databases and replication.

    We learned the meaning of scalability with respect toVLDB and OLTP environments

    We examined several scalability features found in Oracleand SQL Server such as dynamic memory management,

    parallel SQL, query rewrite


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