By Franck Pachot . I’ve described in previous posts how the 12c online datafile move works: your session process do the copy and tells other writers (dbwr and direct-path inserts) to write blocks to both files (old one and new one for blocks that have already been copied). Readers read old file until the copy is completed. The target file…
When you want to do instance caging, you have to set manually CPU_COUNT and to set a resource manager plan. If you By Franck Pachot . only the CPU_COUNT no instance caging will occur. Except during the maintenance window where the maintenance plan is set internally. You don’t want that kind of unpredictable behavior, so the recommandation is to always…
By Franck Pachot . When you want to download the latest patchset of the latest release, 12.1.0.2, you can find two patchsets referenced: 17694377 and 21419221. The short answer is: download p21419221 and add latest PSU and bundle patch. Here is the kind of question that can be raised: Does anyone know why there are two of them? pic.twitter.com/J3ZZ1K13lc —…
By Franck Pachot . The 12c adaptive plan prepares two join methods (Hash Join and Nested Loop), actives the one that has the better cost for the estimated cardinality and computes the point of inflection in cardinality estimation where the best cost changes to the other join method. At execution time, rows are buffered by a STATISTICS COLLECTOR operation in…
By Franck Pachot . When non-CDB has been declared deprecated, I was a bit upset because multitenant with a lone PDB just looks like an overhead of 3 containers instead of one. But with experience I changed my mind. First because the multitenant architecture brings some features that are available even without the option. And second, because this overhead is…
By Franck Pachot . Before 12c, the fixed stats statistics were not gathered automatically. In 12c this has changed: even when you have never gathered fixed objects statistics you can see that you have statistics for X$ tables. That may be better than having no statistics at all, but it doesn’t replace manual gathering at the right time. Documentation First…
By Franck Pachot . Matching the Feature Usage Statistics to licensed options is not always easy. And once a feature usage is recorded, it is usually stored definitively. Let’s see how the multitenant option is recorded there. exec_db_usage_sampling I have a single-tenant database with only one user pluggable database: 16:19:20 SQL> show pdbs CON_ID CON_NAME OPEN MODE RESTRICTED ———-…
By Franck Pachot . Oracle Database 12c introduced the ‘restore from service’ where you can restore and recover by requesting backupsets from the source. With that feature, the duplicate from active can work in the opposite way: instead of asking the source (target) to send the files to the destination (auxiliary) now the destination can do all the job. Let’s…
By Franck Pachot . In multitenant, the spfile parameters at pluggable database level are not stored in the spfile but in the CDB$ROOT table SYS.PDB_SPFILE$ If you open the standby database in read only for reporting, which is one reason to get Active Data Guard option, you may want different optimizer settings suited for reporting. In non-CDB it’s easy: the…
By Franck Pachot . In Multitenant, there are two ways to connect to a pluggable database. This means that if you want to prevent access to a pluggable database you need to revoke two privileges. Privilege Analysis Rather than trying with different combination of privileges there is a clever way to do it in 12c with privilege analysis (remember it’s…
By Franck Pachot . I received a question about multitenant. AWR tables are often raised as an example of Object Links because automatic workload repository is stored only in CDB$ROOT. However, neither the views DBA_HIST… nor the tables WRH$_… are defined as Object Link. Let’s explain on an example: DBA_HIST_SYSSTAT I’ll talk about all those multitenant internals in DOAG 2016…
By Franck Pachot . In multitenant, there are two goals: consolidation within the same container database and isolation of pluggable databases. I see multitenant consolidation as an extension of schema consolidation. What is not possible in schema consolidation, such as public objects name collision, is now possible with pluggable databases. 10 years ago I administrated on a database with high…
