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Testing Oracle on exoscale.ch
My last post came from a discussion at SITB with exoscale. They are doing Cloud hosting with datacenters in Switzerland. In Switzerland a lot of companies cannot host their data outside of the...
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When a query has read 350TB after 73K nested loops
According that you have Tuning Pack, SQL Monitor is the right way to see what a query is currently doing. A query was running for days and the first figure I see is that it has read 350TB. This is not...
View ArticleAdaptive Plan: How much can STATISTICS COLLECTOR buffer?
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...
View ArticleMultitenant dictionary: what is stored only in CDB$ROOT?
Multitenant architecture is about dictionary separation. The idea is that all system metadata is stored only in CDB$ROOT so that space and upgrade time are optimized. Is it entirely true? let’s count...
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Data Guard as a Service
A ‘Data Guard’ checkbox is available for a long time on the Oracle Public Cloud Database as a Service, but it’s only for a few days that it does something: create a service with an database in Data...
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SYS password on Oracle Cloud Service managed database
When you create a DBaaS on the Oracle Cloud services you have to provide an administration password in the database configuration form. You do not need a password to connect to the VM. You use SSH key...
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Which patchset for 12.1.0.2 ?
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...
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DB_FLASHBACK_RETENTION_TARGET may hang your database
DB_FLASHBACK_RETENTION_TARGET is set to keep enough flashback logs to be able to flashback database within the specified retention window. But it’s supposed to be a target only, meaning that on space...
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Extended clusters and asm_preferred_read_failure_groups
When you have 2 sites that are not too far you can build an extended cluster. You have one node on each site. And you can also use ASM normal redundancy to store data on each site (each diskgroup has a...
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Learning and troubleshooting: Follow the path
You query a simple table to get its rows. Did you ever ask yourself how oracle knows which blocks to read from disk? Let’s question everything and follow the path to dictionary, bootstrapping, spfile,…...
View ArticleWhere is the ASM SPFILE?
In the previous blog post, to the question “where is the ASM SPFILE” I answered by running ‘asmcmd spget’. But this is available only if the ASM instance is started. If you have corrupted your SPFILE...
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Oracle on Windows Server Core
If SQL Server, the database for GUI fans, goes to Linux then Oracle, the database for command line fans, can go to Windows. Ok, that’s not new. But I’m not talking about the Windows with media player,...
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Instance Caging and multitenant: do the right setting
When you want to do instance caging, you have to set manually CPU_COUNT and to set a resource manager plan. If you set only the CPU_COUNT no instance caging will occur. Except during the maintenance...
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Large Pages on Windows
In a previous post I’ve installed Oracle on a Windows Server Core. Now I’ll enable large pages. ORA_LPENABLE To let Oracle use Large Pages on Windows, you need to define a registry string...
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CPU_COUNT
When you have less CPU threads than the number of processes that has something to run in CPU, the OS will schedule them to share the CPU resource. Increasing the workload at that point will not...
View Article12c online datafile move and resize
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...
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ASM iostats
A few screenshots and a link here. Sysadmins do not like ASM because they don’t have the tools they like to manage the disks. For example, they don’t want to run SQL queries to check performance, and...
View ArticleWhen changing CURSOR_SHARING takes effect?
I usually don’t advice to set CURSOR_SHARING=FORCE but imagine your application requires it, you forgot it (or tried to do without) on migration and then everything is slow. You want to change it, but...
View ArticleORA-01775: looping chain of synonyms
This error message is misleading. You may encounter it when you expect ORA-00942: table or view does not exist. Let’s explain I’m connected as SCOTT and create a PUBLIC SYNONYM for an object that do...
View ArticleAdaptive Plans and SQL Baselines
I encountered recently an issue with Adaptive Plan and SPM. Documentations says that it works perfectly together but I remembered a presentation from Nelson Calero at UKOUG TECH15 mentioning strange...
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