Much over looked thing while building UAT and DEV databases is it does not model Production database. I'v seen people tend to ignoring unless they are pushed hard to keep UAT and DEV databases as much as close to Production database design, Data distribution and Hawrdware/Software environment.
for e.g. There was an Java Application running on Tomcat - Apache on Solaris 10 on on 64 bit SPARC machines.
1. UAT database was refreshed from export dump instead from Physical Hot/Cold/RMAN backup of Prod. Extent size on UAT and Prod was different. Prod had large fragmentation in some tables,indexes. While UAT did not have as it was refreshed from export dump
2. Statistics were gathered in different way than Production.
3. All database were placed on single Disk array on UAT database. Production has three mirrored copies of Redo logs while UAT has no mirrored redo log.
4. Application was using Connection pooling implemented through java developed code in application only (instead using Oracle's default connection pooling or connection pooling of Weblogic etc)
5. UAT middle tier was using different JDBC driver than Production.
for e.g. There was an Java Application running on Tomcat - Apache on Solaris 10 on on 64 bit SPARC machines.
1. UAT database was refreshed from export dump instead from Physical Hot/Cold/RMAN backup of Prod. Extent size on UAT and Prod was different. Prod had large fragmentation in some tables,indexes. While UAT did not have as it was refreshed from export dump
2. Statistics were gathered in different way than Production.
3. All database were placed on single Disk array on UAT database. Production has three mirrored copies of Redo logs while UAT has no mirrored redo log.
4. Application was using Connection pooling implemented through java developed code in application only (instead using Oracle's default connection pooling or connection pooling of Weblogic etc)
5. UAT middle tier was using different JDBC driver than Production.
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