New type of schema can be created in 18C where user has no password.
CREATE USER username NO AUTHENTICATION;
Schema Only Accounts Oracle Database 18C
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Scalable sequences Oracle Database 18C
Sequence is commonly known oracle object that is used to generate numbers in specified orders. In Oracle 18C new extra words can be defined for sequence creation:
- SCALE | NOSCALE(default)
- EXTEND | NOEXTEND(default)
Cancel SQL statement Oracle Database 18C
In latest version of database 18C instead of killing user session you can cancel its currently running or opened SQL statement using the ALTER SYSTEM CANCEL SQL statement. Continue reading
sqlplus catch and log all ORA- errors
Following article shows how to catch all ORA- statements in sqlplus using clause
SET ERRORLOGGING ON
Indexing NULL for Oracle
General rule for creating indexes in Oracle is following:
- Bitmap indexes – always index nulls
- B*Tree cluster indexes – always indexes nulls
- B*Tree indexes – can’t index data if all indexed columns are NULL
The last one can cause some performance issues but there is trick to index all NULL columns also for B*Tree indexes.
Install Oracle 18C on Oracle Linux 7 (OEL7)
This article presents how to install Oracle 18C on Oracle Enterprise Linux 7 (OEL7).
Read following article how to install Oracle Enterprise Linux 7: Install Oracle Linux 7 (OEL7) (set 8G memory for your virtual machine before proceeding with Oracle software installation).
Code Based Access Control for Definer’s Rights and Invoker’s Rights Oracle Database 12C release 2 (12.2)
In Oracle 12C it’s possible to assign a role to a code procedure/function/package
GRANT role_name TO PROCEDURE|FUNCTION|PACKAGE code_name;
This kind of grant can be executed only by following user:
- SYS
- user with GRANT ANY ROLE privilege
- user who own code and was granted the role with ADMIN OPTION
- user who own code and was granted the role with DELEGATE OPTION
Top three options are commonly know. New option is DELEGATE OPTION. It enables to grant a role to procedure|function|package and nothing more.
Once the role is granted to a code the role is always enabled no matter if the code is created with PRAGMA AUTHID_USER or PRAGMA DEFINER and no matter if owner of the code calls it or other user.
NO_EXPAND USE_CONCAT hints
This article focus on two hints:
USE_CONCAT - The USE_CONCAT hint forces combined OR conditions in the WHERE clause of a query to be transformed into a compound query using the UNION ALL set operator. Generally, this transformation occurs only if the cost of the query using the concatenations is cheaper than the cost without them.
NO_EXPAND - The NO_EXPAND hint prevents the cost-based optimizer from considering OR-expansion for queries having OR conditions or IN-lists in the WHERE clause. Usually, the optimizer considers using OR expansion and uses this method if it decides that the cost is lower than not using it.
NO_EXPAND can be forced by alter session for all statements
ALTER SESSION SET "_no_or_expansion" = TRUE;
Install Fedora 26
This article presents how to install Fedora 26 – Live Workstation version.
I assume you have already downloaded Fedora 26 64 bit Live Workstation(about 1,3 G) and you know how to use VirtualBox 64 bit(100M). Create virtual machine with default settings for Linux Fedora 64 bit. 2CPU, 2GB ram and 64G(includes extra space for Oracle installations) for disk is enough plus increase video memory to 128M. Rest of options you can keep default.
Set autotrace in sqlplus
This article describes how AUTOTRACE works in sql*plus.