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Database Mirroring (DB2) on remote site » History » Revision 12

Revision 11 (chin-yeh, 03/22/2012 10:22 AM) → Revision 12/23 (chin-yeh, 03/22/2012 10:33 AM)

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 h1. Database Mirroring (DB2) on remote site 

 h2. Introduction 

 To mirror production database(s) to remote site, there are a number of approaches: 
 # Use <code>(full)</code> database backup 
 # Use <code>(full + cumulative)</code> database backup 
 # Use <code>(full + delta)</code> database backup 
 # Use <code>(full + cumulative+ delta)</code> database backup - _not recommended because it is too complex_ 
 # Use <code>(full database backup + transaction logs)</code> 

 > the approach 1-4 are described in "Using DB2 incremental backup":http://www.ibm.com/developerworks/data/library/techarticle/dm-0910db2incrementalbackup/ 

 We will only discuss about the last approach, _full + transaction logs_ in the coming sections. Before that, let's do a quick compare for these approaches: 
 ||_.full|_.full + cumulative|_.full + delta|_.full + cumulative + delta|_.full + transaction logs| 
 |*Backup Image Size*|Biggest|Small|Smallest|In between Small and Smallest|Smaller| 
 |*Backup Time*|Longest|Depends on how the data is stored across tablespaces. If all data is stored in one tablespace then it won't make any difference|Depends on how the data is stored across tablespaces. If all data is stored in one tablespace then it won't make any difference|Depends on how the data is stored across tablespaces. If all data is stored in one tablespace then it won't make any difference|Fast| 
 |*Easy To Recover*|Easiest|Easy|Difficult|Very Difficult|Easy| 
 |*Need To Revise Backup Strategies*|No|Yes|Yes|Yes|No| 
 |*Resources Utilization*|High|High to Medium|High to Medium|High to Medium|Low| 
 |*DB is usable after first restored*|Yes|No|No|No|No| 
 |*Functions Used*|backup + restore + rollforward|backup + restore + rollforward|backup + restore + rollforward|backup + restore + rollforward|backup + restore + rollforward + rsync| 


 h2. Full Database Backup + Transaction Logs 

 Below diagram describes how this approach works: 

 !full_transaction_logs_approach.png! 

 _Sample steps:_ 
 # Like any other approaches, you must perform a full database backup _(either offline or online)_ 
 ** e.g.: 
 <pre>$ db2 backup db prod_db online</pre> 
 # Transfer the full backup image to the standby site and perform a database restoration: 
 ** e.g.: 
 <pre>$ db2 restore db prod_db replace history file</pre> 
 # Use the <code>rsync</code> command to do an one way incremental sync from remote (production) site to standby site. 
 ** e.g.: 
 <pre>$ rsync -var --delete db2inst1@db-prod:/home/db2inst1/db2inst1/NODE0000/SQL00001/SQLOGDIR/ /home/db2inst1/db2inst1/NODE0000/SQL00001/SQLOGDIR</pre> 
 # Execute the <code>rollfoward</code> on the standby database: (*do not* include the *complete* option) 
 ** e.g.: 
 <pre>$ db2 rollforward db prod_db to end of logs</pre> 
 # If want to bring up the standby database, just execute this command (_change the database alias_): 
 <pre>$ db2 rollforward db prod_db complete</pre> 

 The biggest advantage of this approach is there's little or no need to revise current backup strategies, however, the mirror database cannot be used until the <code>rollforward</code> process is terminated (_also happens on the other db incremental backup approaches_). 

 h2. Test Tools 

 To test run those database backup