Oracle Database Physical I/O IOPS And Throughput Benchmark
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View ArticleNo Asynchronous I/O When Using Shared Server (Also Known As MTS)
I've recently had a case at a client where it was questioned why a particular application was seemingly not making full use of the available I/O capabilities - in comparison to other databases /...
View ArticleTKPROF’s Argument PDBTRACE
If you run TKPROF without arguments, you get a complete list of its arguments with a short description for each of them (here the output generated by version 18.1.0):read more
View ArticlePartition-Wise Operations – New Features in 12c and 18c
Partition-wise operations are not something new. I do not remember when they were introduced, but at that time the release number was still a single digit. Anyway, the aim of this post is not to...
View ArticleChinar Aliyev's Blog
Chinar Aliyev has recently started to pick up on several of my blog posts regarding Parallel Execution and the corresponding new features introduced in Oracle 12c.It is good to see that obviously...
View ArticleBloom Filter Efficiency And Cardinality Estimates
I've recently came across an interesting observation I've not seen documented yet, so I'm publishing a simple example here to demonstrate the issue.In principle it looks like that the efficiency of...
View ArticleI/O Benchmark Minor Update
I've recently published a new version 1.03 of the I/O benchmark scripts on #333333;">my #336699;">github repository#333333;"> (ideally pick the #336699;">IO_BENCHMARK.ZIP containing all the...
View ArticleCompression Restrictions - Update: Wide Table Compression In 12.1 And Later
I do have a very old post that used to be rather popular here that listed various restrictions related to compression. One of the most obvious restrictions in older versions was that the basic / OLTP...
View ArticleIndexing Null Values - Part 1
Indexing null values in Oracle is something that has been written about a lot in the past already. Nowadays it should be common knowledge that Oracle B*Tree indexes don't index entries that are...
View ArticleIndexing Null Values - Part 2
In the previous post I've demonstrated that Oracle has some problems to make efficient use of B*Tree indexes if an IS NULL condition is followed by IN / OR predicates also covered by the same index -...
View ArticleV$SQL_CS_HISTOGRAMS: What Are the Buckets’ Thresholds?
The contents of the V$SQL_CS_HISTOGRAM view is used by the SQL engine to decide when a cursor is made bind aware, and therefore, when it should use adaptive cursor sharing. For each child cursor, the...
View ArticleMIN/MAX Optimization and Asynchronous Global Index Maintenance
In this short post I would like to point out a non-obvious issue that one of my customers recently hit. On the one hand, it’s a typical case where the query optimizer generates a different (suboptimal)...
View ArticleSingle Value Column Frequency Histogram Oracle 12c and later
It is hopefully in the meantime well known that Oracle has introduced in version 11g a new algorithm to gather statistics on a table that no longer requires sorting for determining the critical Number...
View Article12.2.0.1 And Later Support (Limited) Extended Stats On Virtual columns /...
I do have a demo as part of my optimizer related workshops that shows the restriction / limitation of DBMS_STATS not supporting extended statistics on virtual columns / group of expressions, so for...
View ArticleNew Parallel Distribution Method For Direct Path Loads
Starting with version 12c Oracle obviously has introduced another parallel distribution method for direct path loads (applicable to INSERT APPEND and CTAS operations) when dealing with partitioned...
View ArticleOracle 12c – pre-built join index
By Franck Pachot. This post is part of a series of small examples of recent features. I’m running this in the Oracle 20c preview in the Oracle Cloud. I have created a few tables in the previous post...
View ArticleOracle 12c – peak detection with MATCH_RECOGNIZE
By Franck Pachot. This post is part of a series of small examples of recent features. I’m running this in the Oracle 20c preview in the Oracle Cloud. I’ll show a very basic example of “Row Pattern...
View ArticleOracle 12c – reorg and split table with clustering
By Franck Pachot. In this series of small examples on recent features, I have imported in a previous post, the statistics of covid-19 per day and per countries. This is typical of data that comes as a...
View ArticleOracle 12c – global partial index
By Franck Pachot. We have an incredible number of possibilities with Oracle. Yes, an index can be global (indexing many partitions without having to be partitioned itself on the same key) and partial...
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