tuning
13.01.2016

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 […]


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12c
29.10.2015

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 […]


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SECURITY
11.10.2015

Secure your database (part 1)

I’ve already showed you, how to escalate privileges in Oracle Databases. https://blog.ora-600.pl/2013/04/02/privilege-escalation-in-oracle-11gr2-part1/ https://blog.ora-600.pl/2014/12/23/simple-technics-of-privilege-escalation-part2-dbasysdba/ The question is – how to secure your database, if you don’t have EE or possibility to buy Oracle Database Vault or Oracle Advanced Security. Well – there’s always a DBA creativity ­čśë For example – if you want to secure the […]


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[PL] Browar z Wyroczni─ů
04.09.2015

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 […]


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RICO
03.09.2015

RICO

I’ve started the project called RICO – the tool, written in C++ for last resort data recovery. It can be used to extract data from corrupted datafiles and dump them in the form of text files. It is in the early development stage right now and the functionalities are narrowed to: Dump regular and partitioned […]


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I/O
17.07.2015

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 […]


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12c
25.05.2015

12c: duplicate pluggable database without READ ONLY mode

At the beginning we have to prepare parameter file for the new instance Start the instance in nomount Since I want to duplicate the database in active mode I will register it in LISTENER. To achieve this I have to add the following lines to the listener.ora Now we can perform active database duplication with […]


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ASM
14.05.2015

DBA: migrate database to ASM

Let’s try to migrate database to ASM diskgroup without big maintenance window. I have database and ASM (11.2.0.4) – the database is prepared to migration: We will use recoverable copy of database to migrate to ASM. The first run of this script will create copy of datafile on ASM: Subsequent executions of this script will […]


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ASM
14.05.2015

Install ASM manually using response file

I have configured two devices for ASM – one with ASMLib and one with UDEV: I have downloaded 11.2.0.4 grid infrastructure binaries and prepared response file: Of course in production environment you have set different groups for security reasons. If you think that you can ignore security, read my articles regarding privilege escalations: https://blog.ora-600.pl/category/oracle/security/ With […]


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