Exadata – direct path write temp and flash disks

Some time ago one of my students asked me if temp segments are being written to flash disks on Exadata… Well I wasn’t sure ­čÖé But recently I had some time to check it. Let’s create some query that will generate temp segment: Great. Now we have to do some tracing at the cell servers […]

Read more

Sparc M7 vs Intel and P8

I had a pleasure to work with my colleagues from Oracle – Rados┼éaw Kut and Krzysztof Marciniak – at comparing the performance of In-Memory queries between Sparc M7, Intel┬« Xeon┬« X5670 and Intel┬« Xeon┬« E5-2699. You can find results of our findings in this presentation: https://www.oracle.com/webfolder/s/delivery_production/docs/FY16h1/doc17/DB12c-on-SPARC-M7.pdf Following their methodology I’d like to present appropriate results […]

Read more

Oracle SPARC M7 – tracing DAX with DTrace and busstat

Thanks to Oracle I had a possibility to test the new Sparc M7 with DAX coprocessors to boost In-Memory performance. You can read about it here and here My first thought was – how to check if and when the DAX coprocessors are being used? When you have a POC for Exadata, you want to […]

Read more

oracle dblinks – performance considerations

Let’s imagine the following situation – you have a table called EMPLOYEES_TMP which is a global temporary table with a variable number of rows – totally nondeterministic. And there is a query which runs very often to compare primary key values between this table and a remote one (which is basically the same but not […]

Read more

Oracle 12c – internals of threaded execution

At UKOUG Tech’15 (Super Sunday) there was a session called "12c: A Closer Look at the Multi-Process Multi-Threaded Model for Oracle on Linux/Unix" by Markus Flechtner. Since then I can’t stop thinking about the performance of this feature. Why Oracle decided to provide it? I did some tests regarding sort operations and threaded execution was […]

Read more

Oracle 12c: PRAGMA UDF – the truth

Let’s check, why PRAGMA UDF makes execution faster, then regular function. C function responsible for calling a PL/SQL code from SQL is called "plsql_run": Now let’s try to create a new HR session and create a simple function which will multiple values by 2: From other terminal I will connect to the HR session with […]

Read more
[PL] Browar z Wyroczni─ů

Jak smakuje Browar z Wyroczni─ů

I by┼éo tak, ┼╝e 31 dnia miesi─ůca sierpnia roku 2015, spotkali si─Ö┬áentuzja┼Ťci┬áWyroczni w posiad┼éo┼Ťci AVIVA. I by┼éo tak, ┼╝e dzier┼╝─ůc┬ákufle┬á– po brzegi browarem wype┼énione – zasiad┼éo wielu aby pos┼éucha─ç kilku, kt├│rzy chcieli si─Ö┬áprzemy┼Ťleniami swoimi podzieli─ç. I sta┼éo si─Ö tak, ┼╝e admin przepija┼é do dewelopera a deweloper do admina i pospo┼éu dyskusja toczy┼éa si─Ö wartka a […]

Read more

12c – SQL plan directives

One of the new CBO features in database 12c is "sql plan directives". The main purpose of this functionality is to deliver better adaptive plans if object statistics does not reflect the reality. Quoting after documentation During SQL execution, if a cardinality misestimate occurs, then the database creates SQL plan directives. During SQL compilation, the […]

Read more

db file scattered read – MBRC and ASYNC IO on linux

Recently one of my students asked me if there is any correlation between the AU size in ASM diskgroup and parameter db_file_multiblock_read_count. I made some tests but results are very strange. I have 4 same tables, located in 4 different diskgroups: All tables are smaller then a hidden parameter "_small_table_threshold" so table access full on […]

Read more
12c (Spatial)

12c: Spatial Vector Acceleration

There is a new feature in Oracle Spatial 12c, called "Spatial Vector Acceleration". According to Oracle: One of the most notable improvements with Oracle Spatial and Graph 12c can be seen in performance increases in vector data operations. Enabling the Spatial Vector Acceleration feature (available with the Spatial option) dramatically improves the performance of commonly […]

Read more

Oracle 11g & 12c: tunning the sort and hash operations

Hash and sort operations are perfomed in PGA. Quoting after the documentation: A sort operator uses a work area (the sort area) to perform the in-memory sorting of a set of rows. Similarly, a hash-join operator uses a work area (the hash area) to build a hash table from its left input. If the work […]

Read more

Oracle CBO. Query Transformer

Oracle Cost Based Optimizer consists of three main components: Query Transformer, Esitmator, Plan Generator. In this article I will try to show you some interesting features of the first component ÔÇô Query Transformer. This component has some very powerful features and most of them remain in shadows, unrevealed while other new features gains all the […]

Read more

library cache: mutex X i CURSOR_SHARING=FORCE:

Prowdz─ůc niedawno optymalizacj─Ö wydajno┼Ťci jednego RACa, natkn─ů┼éem si─Ö na ciekawe zachowanie w trakcie parsowania zapyta┼ä odwo┼éuj─ůcych si─Ö w predykacie do typu TIMESTAMP – niecodzienne zachowanie dotyczy ustawienia CURSOR_SHARING=FORCE i bazy oraz Problem opis┼éem na forum GoldenLine – je┼Ťli spotkali┼Ťcie si─Ö z podobnym problemem lub znale┼║┼Ťcie jakiego┼Ť patcha – zach─Öcam do podzielenia si─Ö t─ů […]

Read more
1 2

Contact us

Database Whisperers sp. z o. o. sp. k.
al. Jerozolimskie 200, 3rd floor, room 342
02-486 Warszawa
NIP: 5272744987
+48 508 943 051
+48 661 966 009

Newsletter Sign up to be updated