When 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...
View ArticleODA X6-2S and ODA X6-2M for EE and SE2
After the announcement of the death of SE1 and SE we wondered what Oracle will do for Small and Medium Enterprises and entry level products. The answer was postgres the Oracle Cloud Services, but...
View ArticleClik here to view.
Question is: upgrade now to 12.1.0.2 or wait for 12.2 ?
Let’s look at Release Schedule of Current Database Releases (Doc ID 742060.1) 12.2.0.1 is planned for 2HCY2016 on platforms Linux x86-64, Oracle Solaris SPARC (64-bit), Oracle Solaris x86-64 (64-bit)....
View ArticleStatspack Idle Events
When you don’t have Enterprise Edition + Diagnostic Pack, you cannot use AWR but you can, and should, install Statspack. Statspack is still there, but unfortunately do not evolve a lot. The most...
View ArticleScript to suggest FK indexes
In Oracle, when the referenced key is deleted (by delete on parent table, or update on the referenced columns) the child tables(s) are locked to prevent any concurrent insert that may reference the old...
View ArticleCompare source and target in a Dbvisit replication
You’ve setup a logical replication, and you trust it. But before the target goes into production, it will be safer to compare source and target. At least count the number of rows. But tables are...
View ArticleClik here to view.
Oracle Multitenant feature name
We all know what is the multitenant option: a container database (CDB) with multiple user pluggable databases (PDB). This requires Enterprise Edition plus option. But you can use the same architecture...
View ArticleNulls in composite keys
Comparison of NULL can be misleading and it’s even worse for unique constraint validation. Having partial nulls in a composite key can be tricky because the SQL ANSI specification is not very easy to...
View ArticleOracle Public Cloud patch conflict
This morning I wanted to test a patch (18633374) in the Oracle Cloud Service. The DBaaS was created as an ‘Enterprise Edition Extreme Performance’ which comes with all options, including multitenant...
View ArticleAMM and ASMM derived parameters
The latest DBA Essentials Workshop training I’ve given raised a question about PGA_AGGREGATE_LIMIT. The default depends on PGA_AGGREGATE_TARGET. So how is it calculated in AMM where...
View ArticleClik here to view.
ODA X-6 log file sync with NVMe flash
The new ODA X-6 has been announced last month with two smaller configurations and smaller prices: 2S and 2M. Small, but high performance configuration: all SSD, and I/O transfer optimized for Flash...
View ArticleClik here to view.
Redo log block size on ODA X6 all flash
On the Oracle Database Appliance, the redo logs are on Flash storage (and with X6 everything is on Flash storage) so you may wonder if we can benefit from 4k redo blocksize. Here are some tests about...
View ArticleClik here to view.
Large Pages and MEMORY_TARGET on Windows
In a previous post about enabling large page on Windows Server, I explained that it’s possible to use large pages with Automatic Memory Management (AMM, where sizing if SGA and PGA is automatic with...
View ArticleClik here to view.
Exadata X-5 Bare Metal vs. OVM performace
The Exadata X5 can be installed Bare Metal or Virtualized. The latter one, Oracle VM allows to create multiple clusters on one machine, is more complex for installation and for storage capacity...
View ArticleOracle serializable is not serializable
Did you know that when you set isolation level to SERIALIZABLE, it is not serializable but SNAPSHOT? This isolation levels is lower than serializable. I’ve never thought about it until I read Markus...
View ArticleExadata X-5 Bare Metal vs. OVM load testing
In a previous post I tried to compare a single thread workload between Exadata X5 Bare Metal and Virtualized. The conclusions were that there is no huge differences, and that this kind of comparison is...
View ArticleMultitenant internals: how object links are parsed/executed
I had a comment on object links internals when creating a sharing=object view on GV$SESSION. Before posting about this specific case, I realized that I’ve never explained how a query on an object link...
View ArticleMultitenant internals: object links on fixed tables
The previous post partly answered to the original question (why an object link to V$SESSION is refreshed only every 30 seconds): recursive queries on shared=object views. Now let’s see what is...
View Article