![DB
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AP 1 AP n
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[Figure 1, High Availability secured in a 2-Way Replication System] [Figure 2, Scalability improved in a 2-Way Replication System]
What is Replication?
Replication is a technique for sending information about the changes to the contents of
a single database over a network to one or more other databases.
The Purpose of Replication
♦ Secures High Availability
♦ Improves performance and scalability by Load-balancing
♦ Minimizes Data Loss in the Event of a Physical Outage or Disaster](https://image.slidesharecdn.com/altibase8replicationpart1overview-160126071132/85/Altibase-8-replication-part1-overview-3-320.jpg)
[Altibase] 8 replication part1 (overview)
- 1. Non-Stop Service System Minimizing Downtime and Maintaining the system availability up to 100% Planed Downtime – Regular inspection & System upgrade/patch Executing Switch-Over : Main modification of normal service Unplanned Downtime – Failure in some systems Executing Fail-Over : Main modification of urgent service High Availability / HA Non-stop system or the availability of its contents five 9 (99.999%) Various techniques exist at the level of S/W and H/W HA of DBMS Activates by synchronizing the databases through nodes Techniques are different depending on the architecture of parallel database
- 2. Categories Shared Nothing Architecture Shared Disk Architecture Shared resources There is no shared resources Disk Data synchronization Replication through network Sharing disk Performance* Fast performance as there is no shared resources Performance reduced by complicated Processing(2PC/3PC) of shared resources System costs* Low costs (Local disk & Network) High costs(Shared storage facilities) Distance* There are not too much harsh in a long distance as the general TCP based network is used There is a restriction of distance as the dedicated network of high cost for sharing disk is required Data conformity* The extra consideration is required to control the data inconsistency in each node for the features of network replication The data conformity is guaranteed in each nodes as the data is shared Critical Failures Unable to synchronize nodes when there is a network failure Entire services in system do not work when there is a disk failure Appropriate system Faster performance is more required than data conformity Data conformity is more required than performance Relevant DBMS technique Replication RAC (Real Application Cluster) Relevant DBMS ALTIBASE HDB, DB2, MS-SQL, ORACLE, SYBASE ORACLE, DB2 ▣Trade-off between “performance, system establishment costs, distance” and “ data conformity”
- 3. DB SERVER main DB SERVER sub replication AP 1 AP n Fail-Over AP 1 APm+1AP m AP n DB SERVER main DB SERVER sub replication [Figure 1, High Availability secured in a 2-Way Replication System] [Figure 2, Scalability improved in a 2-Way Replication System] What is Replication? Replication is a technique for sending information about the changes to the contents of a single database over a network to one or more other databases. The Purpose of Replication ♦ Secures High Availability ♦ Improves performance and scalability by Load-balancing ♦ Minimizes Data Loss in the Event of a Physical Outage or Disaster
- 4. Main Features Description TCP/IP Network-Based Because the only facility that is required for replication is a network connection, no additional expenses are incurred. Replication over long distances is possible, depending on network performance (a Gigabit LAN is recommended) Heterogeneous OS Support Replication is possible between heterogeneous operating systems, and regardless of the number of OS bits (32 or 64) or CPU endian Integrated Replication High Performance as the replication module is completely integrated with DBMS No additional ALTIBASE HDB packages are required for replication ALTIBASE HDB can be flexibly used depending on the user’s requirements Redo Log-based Redo logs are sent in real time by records Table-Based Management Replication is managed by table Table can be added to replication or deleted from replication while database is running Two Modes: LAZY and EAGER Supports both LAZY(Async) and EAGER(Sync) replication modes High-Speed Replication In LAZY mode, the replication is executed with at least 95% of master transactions speed while not affecting the master transaction (Measured on a UNIX system in a Gigabit LAN environment) Up to 32-Way Replication A single ALTIBASE HDB node can have up to 32 replication objects Load distribution across heterogeneous systems is supported
- 5. Main Features Description Point-To-Point Replication Replicating 1:1 only between nodes that it does not transfer to other nodes Network Fault Detection ALTIBASE HDB provides dedicated threads to detect physical network faults Automatic Recovery The time point at which replication was most recently performed is recorded. In the event of network failure, replication resumes automatically once the network connection is restored. Support for Multiple IPs If two or more IP addresses are assigned to a single replication, replication can automatically switch to the other IP address in the event of a network fault, thus increasing the availability of replication. Control via SQL Interface All commands required in order to use and manage replication have an SQL interface thus it is convenient to use. Data Conflict Resolution Methods Three (3) schemes and one (1) utility are provided to resolve data conflicts. Additional Functions Replication can be used to clone (i.e. copy the entire contents of) tables. If the active node fails, offline replication can be conducted to access the redo log files on the node that failed and resume replication on the standby node.