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RDBMS Server

Oracle RDBMS Server Articles

Yet another alert log puzzle

A handy alert log is invaluable for troubleshooting database problems. A RAC database has multiple alert logs.
I prefer to monitor them through a single table.

"A master failing to make an entry in the vessel's official
logbook as required by this part is liable to the Government for a
civil penalty of $200.

United States Code. Title 46 - Shipping. Subtitle II -Vessels and seamen, Part G - Merchant seamen protection and relief. Chapter 1113 -Official logbooks.

How meticulously do you keep your book log, Captain?
Luckily for us, our databases are as much ships as they are first mates. They are intelligent enough to keep their own records. And those logs are as important as vessel logs of the past, because the information carried by an early 21st century database could be easily worth more than 1450 tons of tea carried by Cutty Sark in 1870 en route from Shanghai to London.

As Oracle does all the mundane work, our role becomes more creative - to inspect and properly use the gathered information.

Experimenting with the continous mining

cbruhn2's picture

Today I have been experimenting with the new feature of continous mining with logmnr.

My setup

  • Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production With the Partitioning, OLAP and Data Mining options
  • ALTER DATABASE ADD SUPPLEMENTAL LOG DATA or we don't see the funny things in the redologfiles
I now starts the logminer session in one window with :
[code]
BEGIN
dbms_Logmnr.Start_Logmnr(StartTime => SYSDATE - 1 / 24, Options => dbms_Logmnr.dict_From_OnLine_Catalog + dbms_Logmnr.Continuous_Mine);
END;
/

SELECT *
FROM v$Logmnr_Logs;

Strange behavior from resetlogs.

cbruhn2's picture

During a test of some backup setup with rman I ran into problem running the restore / recover command.

Securing Your Database: A simple Brute Force Blocker

Natalka Roshak's picture

If you've had to change a Unix password, you know that most systems won't let you use just anything as a password - your password must be a minimum length, and must not be too easy to guess or brute-force. Oracle doesn't come with this capability installed out of the box, but Oracle 8 and above let DBAs define a custom function to complexity-check user passwords. Oracle provides a default password verification function to do some basic checking, although DBAs need to know about it and install it manually.

Using Oracle's recycle bin

Natalka Roshak's picture

One of the many new features that Oracle 10g introduced is the recyclebin. When enabled, this feature works a little bit like the familiar Windows recycle bin or Mac Trash. Dropped tables go "into" the recyclebin, and can be restored from the recyclebin. OraFAQ has already published an article covering the basics; in this article, I'll cover some of the more subtle aspects of the recyclebin.

Logical vs Physical Standby database

Logical vs. Physical Standby databases
Submitted By Rama Subramoniam

A Quick Primer

Standby databases, in a nutshell, acts as a failover for our mission critical production databases. When production database crashes, applications can quickly switchover to the stand by databases.

Oracle provides two types of standby databases:

1. Physical Standby Database

Standby database is called “physical” if the physical structure of stand by exactly matches with stand by structure. Archived redo log transferred from primary database will be directly applied to the stand by database.

Removing duplicate indexes

Indexes are used to speed up data access by SQL statements, but there is no free lunch as each additional index increases:

  • The time needed to perform DML (Insert/Update/Delete) operation on the table (because additional index entries must be updated).
  • The enqueue time (during DML the corresponding index entries are locked decreasing the ability of parallel updates and causing transactions, issued by another session(s) to wait.
  • The generated UNDO volume.
  • The disk space needed to store the index information.

LEARNING TO LOVE LOBS

Natalka Roshak's picture

LOBs, or Large OBjects, are Oracle's preferred way of handling and storing non-character data, such as mp3s, videos, pictures, etc., and long character data. Binary large objects, or BLOBs, and character large objects, or CLOBs, can store up to terabytes of data - much more than the paltry 4000 bytes permitted in a varchar2 column. LOBs and CLOBs offer DBAs and developers great flexibility and storage space; the tradeoff is that they're a bit clunkier to handle.

The first thing to know about LOBs is that there are two basic types: external LOBs, which are stored outside the database, and internal LOBs, which are stored in the database. External LOBs are of the BFILE datatype; essentially, the database stores a pointer to the LOB's location in the file system. As such, they can't participate in transactions, and access is read-only. This article will deal with internal LOBs.

Undo the past with Oracle's Flashback Technology

Pankaj Chandiramani's picture

Flashback Recovery is a new enhancement to the 10g database for the DBA's toolkit. Effectively, it's an "Oh shit!" protection mechanism for DBAs as it reduces recovery time from hours to minutes. Ask any DBA about the main cause of application outage - other than hardware failure - and the answer will be "human error". Such errors can result in logical data corruption and can bring down the complete system. Part of being human is making mistakes. Without advance planning, these errors are extremely difficult to avoid, and can be very difficult to recover from. Typical user-errors may include the accidental deletion of valuable data, deleting the wrong data, or dropping the wrong table.

Using the power of DBMS_JOB.SUBMIT

Natalka Roshak's picture

Some DBAs complain that Oracle's pre-10g job queue interface is lacking. Unlike cron or Windows Scheduler, pre-10g Oracle doesn't provide a mechanism to schedule jobs to run twice a week, on the first of the month, etc.