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Database Feed

Oracle Database, Oracle 10g, Oracle 11g, Oracle XE, Oracle RAC, Oracle Instant Client, Oracle Data Guard and Oracle Exadata resources, news, and support articles.

CPUSPEED Slowing you down?

I often come across systems where the cpu clock speed has been lowered due to cpuspeed. Here is how to up the clock speed on all the cpus with one command. The box I was working on was a dual core 2 cpu box. Here is what the clock speed of the cpus was running [...]

Physical Logical Oracle Database Limits

Physical Database Limits

Item

Type of Limit

Limit Value

Database Block Size

Minimum

Physical Logical Oracle Database Limits

Physical Database Limits

Item

Type of Limit

Limit Value

Database Block Size

Minimum

Final/Source Level forecasts in ORDF

A common misconception in Retail Forecast is that the forecast should always be generated at the lowest level, i.e. per SKU, store and day. This approach is no good when working with real data. Most Retailers have SKUs which have sparse sales. E.g. 5 - 10 sold items per week. There is no way you can statistically forecast such a time series.

The way round this problem is to aggregate your data to a higher level where the density is significant. E.g. at week or product category level. There are two problems with this approach:

Why I don't trust deferrable constraints

I don't like deferred constraints. I don't like deferrable constraints either, because there is the risk of someone making them deferred.

There's a Pythian blog on one potential corruption pitfall where you can end up with duplicate primary keys.

Date format tolerance

This is just a little ditty to remind me which date format mask is more tolerant.

SQL> select to_date('21-03-2011','dd-mon-yyyy') from dual;
select to_date('21-03-2011','dd-mon-yyyy') from dual
*
ERROR at line 1:
ORA-01843: not a valid month

SQL> select to_date('21-mar-2011','dd-mm-yyyy') birthday from dual;

BIRTHDAY
-------------------
21-03-2011 00:00:00

1 row selected.

Note that it accepts 'MAR' when using the MM format, but not numerics when using the MON format.

Rolling partition and global index coalesce

Resolving one of performance issues I figure out that primary key index is much bigger that it should be. Most of database activity is inserting data into partitioning table using some date field as a partitioning key. Rows can be inserted to every partition not only to most recent one. Daily job is dropping one oldest partition per day. Unfortunately primary key index is not partitioned and is maintained during partition drop as a global index.

The Guerilla Hack Chronicles: Dancer as an Ad-Hoc Web Server

Let’s say you want to serve static http content from a machine. The sensible thing to do would be to install Apache/Nginx/Lighttp. But let’s say — because of insane configuration, red tape, cruel whims of the gods — that you can’t do the sensible thing. Fortunately, there’s a few aces you can pull from out [...]

Instant Tweets for Any Website

Say there a website you would like to tweet directly from. Not via a Twitter client, not using a service like Yoolink, not through a Firefox plugin. No, you really want to be able to have a honest to God “Tweet this” input field on the website itself. It’s a strange requirement, for sure, but [...]

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