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7 votes
3 answers
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How can a datapump export have its resource usage limited on windows?

Doing an export of a number of users causes high CPU and I/O usage. I can mitigate the effects of the CPU usage using Resource Manager and setting the export session to a low priority group, but how ...
Leigh Riffel's user avatar
  • 23.8k
22 votes
2 answers
40k views

What is the difference between MySQL VARCHAR and TEXT data types?

After version 5.0.3 (which allowed VARCHAR to be 65,535 bytes and stopped truncating trailing spaces), is there any major difference between these two data types? I was reading the list of ...
Derek Downey's user avatar
  • 23.4k
25 votes
3 answers
19k views

Is it common practice to mix InnoDB and MyISAM tables on same server?

I've got a single database of about 4.5GB running on a server with 8GB RAM. The vast majority of the tables are MyIsam (about 4.3GB), but I'm soon going to be converting some of them to InnoDB. (It's ...
Derek Downey's user avatar
  • 23.4k
4 votes
2 answers
38 views

What can I do to find out since which release a given DBMS supports a feature, function, etc?

It is rather easy to find links describing a feature. In most cases there is no hint in which release the feature was introduced. Often the last resort is to google for the feature in combination ...
bernd_k's user avatar
  • 12.2k
10 votes
2 answers
7k views

What is the meaning of DOP in the context of SQL Server?

What is the meaning of DOP in the context of sql server?
olle's user avatar
  • 1,027
12 votes
1 answer
3k views

What is the impact of changing the index creation memory setting in SQL Server?

I am trying to create some indexes a SQL Server 2008 database but am getting the following error message. Msg 8606, Level 17, State 1, Line 1 This index operation requires 1024 KB of memory per ...
olle's user avatar
  • 1,027
3 votes
1 answer
462 views

How to get the Oracle Text Index's underlying Virtual XML Document?

The Oracle Text Reference 10g states that when we index our table using multi-column datastore, the system concatenates the text columns, tagging the column text, and indexes the text as a virtual XML ...
Gan's user avatar
  • 378
32 votes
1 answer
61k views

INT(5) vs SMALLINT(5): numbers in parenthesis after the numeric type

In MySQL table definitions is there a different between INT(5) and SMALLINT(5)? Or do they both represent the same size?
BenV's user avatar
  • 4,883
7 votes
2 answers
8k views

SQL Server 2008 log files have minimum sizes, what gives and how do I make them smaller?

Ok, to start with, I screwed up when I created the databases, using a create script roughly like so: (artificial linebreaks and names/paths for wrapping purposes) CREATE DATABASE [EXAMPLE] ON ...
jcolebrand's user avatar
  • 6,354
8 votes
1 answer
1k views

How can a datapump export have its resource usage limited on linux?

Doing an export of a number of users causes high CPU and I/O usage. I can mitigate the effects of the CPU usage using Resource Manager and setting the export session to a low priority group, but how ...
Leigh Riffel's user avatar
  • 23.8k
18 votes
3 answers
14k views

What other databases have a feature similar to Oracle's Flashback Query?

I am interested to know what other databases have features similar to Oracle's Flashback Query. It would seem that any database that supports MVCC could have the feature, but which do? SO has this ...
Leigh Riffel's user avatar
  • 23.8k
53 votes
8 answers
158k views

How do I shrink all files quickly for all databases?

In SQL Server (2008 in this case) how can I quickly shrink all the files, both log and data, for all databases on an instance? I could go through SSMS and right click each and choose Tasks -> Shrink, ...
jcolebrand's user avatar
  • 6,354
4 votes
2 answers
2k views

How do I stop refresh conflicts between Proactive Caching of facts and timed refresh of Dimensions in a SQL Server Analysis Service 2005 OLAP cube?

I have a SSAS 2005 OLAP cube which we've very nearly made into a ROLAP cube using a mixture of proactive caching for the fact partitions and timed refreshes for the dimension data. There are two fact ...
ScottCher's user avatar
  • 642
13 votes
2 answers
7k views

How do I change the instance name in MS SQL 2005 without installing a new instance?

I have an instance that really has nothing on it, it's merely been installed (it was intended for one project, but that never actually got done on this server, the project was done in duplicate on ...
jcolebrand's user avatar
  • 6,354
21 votes
4 answers
92k views

Can I change the SID of an Oracle database?

The Server is Oracle Database 11g Enterprise Edition Release 11.1.0.7.0 - 64bit Is there an easy & quick way to change the SIDs of the test databases on the server? Dropping & recreating of ...
bernd_k's user avatar
  • 12.2k
28 votes
4 answers
69k views

How to change SQL Server collation

How could I change the SQL Server 2008 R2 Express Default Collation for the whole server and a particular database? Is there a way to do it using visual interface of SQL Server Management Studio? In ...
rem's user avatar
  • 1,555
7 votes
2 answers
16k views

Can I use OpenLDAP to authenticate users in Oracle?

I like to use OpenLDAP to authenticate my Oracle users. It should be possible to fetch at least the password from the directory. There appearently is something for the Oracle LDAP servers, but would ...
Sebastian Roth's user avatar
73 votes
3 answers
43k views

What are the drawbacks with using UUID or GUID as a primary key?

I would like to build a distributed system. I need to store data in databases and it would be helpful to use an UUID or a GUID as a primary key on some tables. I assume it's a drawbacks with this ...
Jonas's user avatar
  • 32.8k
13 votes
3 answers
7k views

Dynamic SQL in MySQL stored routines

According to the restrictions on stored routines and triggers, dynamic sql cannot be used (restriction lifted for stored procedures in version 5.0.13 and later). Why is this limitation in place? And ...
Derek Downey's user avatar
  • 23.4k
19 votes
6 answers
39k views

What is the recommended RAID configuration for an Oracle database?

RAID (Redundant Arrays of Inexpensive Disks) comes with different configurations (RAID-0, RAID-1...). What is the recommended RAID configuration that I should set up and use when installing an Oracle ...
Eddie Awad's user avatar
7 votes
1 answer
2k views

What are some important MySQL status variables to keep an eye on? [closed]

I'm a fairly new DBA with a programming background. As such, I like to build tools to manage tasks to help me familiarize myself with the intricacies of a technology. In this case, I am managing ...
Derek Downey's user avatar
  • 23.4k
15 votes
3 answers
3k views

Speeding up conversion of MyISAM to InnoDB

I've got a mysql 5.1 server with a database of approximately 450 tables, taking up 4GB . The vast majority of these tables (all but 2) are MyIsam. This has been fine for the most part (don't need ...
Derek Downey's user avatar
  • 23.4k
28 votes
3 answers
38k views

Code to simulate deadlock

I am testing my application I need some code that stable simulates the deadlock on database site (sql script if possible). Thank you. ADDED: Reproducing deadlocks involving only one table
garik's user avatar
  • 6,702
13 votes
2 answers
4k views

Security for Application Developers doing PL/SQL work in Oracle

How do you handle the lack of Schema level privileges in Oracle? Oracle’s security architecture works well for applications that only need object level privileges and it works well for DBAs that need ...
Leigh Riffel's user avatar
  • 23.8k
6 votes
1 answer
142 views

Where to put a database in case of IP failover?

I understand that to achieve some level of availability of an online application it is possible to organize an environment with a redundancy using an IP failover mechanism and switching between ...
rem's user avatar
  • 1,555
29 votes
4 answers
17k views

Why is OS authentication considered poor security for Oracle databases?

Oracle is deprecating OS authentication according to the Oracle Database Security Guide, which says Be aware that the REMOTE_OS_AUTHENT parameter was deprecated in Oracle Database 11g Release 1 ...
Leigh Riffel's user avatar
  • 23.8k
7 votes
3 answers
3k views

Online resource for writing Access SQL statements [closed]

I am looking for an online resource for writing Access SQL statements. I write queries using SQL because the UI puts limitations on what can be queried. I have been using w3schools for reference, ...
Move More Comments Link To Top's user avatar
10 votes
2 answers
6k views

Why can't I read Oracles CLOB columns via SQL-SERVER 2008 linked server?

I want to access data in an Oracle 11g database from SQL-Server 2008 I set up a linked server and when I execute select * from [Link_server_name]..Oracle_schema.Oracle_table and Oracle_table ...
bernd_k's user avatar
  • 12.2k
9 votes
2 answers
9k views

Is it better to store calculated values or recalculate them on request? [duplicate]

Possible Duplicate: Storing vs calculating aggregate values At an old job, we had this database, it wasn't normalized rigth, some tables wheren't used anymore, it was patch after patch. In ...
eiefai's user avatar
  • 1,874
6 votes
2 answers
482 views

different login credentials based on user

I run a PHP symfony-framework web app for my company and it uses a single database login for all connections, whether the user is an admin or a client. I know that higher security systems often use ...
Patrick's user avatar
  • 4,229
8 votes
2 answers
1k views

Is this a new common pattern in Oracle Where exists ( Select NULL FROM...)?

Years ago, it was common to write where exists (Select * from some_table where some_condition) Last year I noticed that many t-sql scripts switched to using the number 1 instead of the star where ...
bernd_k's user avatar
  • 12.2k
1 vote
1 answer
167 views

version controll application/system for mysql databases [duplicate]

Possible Duplicate: Keeping track of schema changes Hello, How do you keep your mysql database schema under version control.
Gabriel Solomon's user avatar
32 votes
9 answers
39k views

How do you version your Oracle database changes?

I am interested to know what methods other people are using to keep track of changes made to the database including table definition changes, new objects, packages changes, etc. Do you use flat files ...
Leigh Riffel's user avatar
  • 23.8k
15 votes
5 answers
16k views

Does it make sense to use SQL Server's bracket notation in hand written code?

Code generators tend to be simpler when they generate output using the new Microsoft bracket notation ([]) for nearly everything. When I first saw it, I though wow a reincarnation of the somewhat ...
bernd_k's user avatar
  • 12.2k
0 votes
3 answers
224 views

What database platform better at scaling? [closed]

I am planning a for a database that i expect will be very big in terms of number of records rather than tables and batabases. My Question is what product (i.e, SQL 2008, Cassandra, Azure) handles ...
Sevki's user avatar
  • 533
19 votes
4 answers
12k views

Task scheduler for SQL Server Express

I have an ASP.NET MVC app which works with database under SQL Server 2008 R2 Express edition. There is a need to perform a regular task on updating some records in the database. Unfortunately the ...
rem's user avatar
  • 1,555
173 votes
6 answers
169k views

Guid vs INT - Which is better as a primary key?

I've being reading around reasons to use or not Guid and int. int is smaller, faster, easy to remember, keeps a chronological sequence. And as for Guid, the only advantage I found is that it is ...
BrunoLM's user avatar
  • 3,463
7 votes
2 answers
154 views

Is there a good "rule of thumb" for translating EXPLAIN cost to (wall-clock) runtime?

From time to time, consumers of my database processes will ask for an estimate of when a given task will be done. While I feel like I know how to read an EXPLAIN in most database engines, I have ...
TML's user avatar
  • 1,364
25 votes
3 answers
5k views

Which collation should I choose for a muiti-language website?

Does a collation have any influence over a query speed? Does the size of a table change depending of the collation? If I want to build a website that must support all possible languages (lets take ...
BrunoLM's user avatar
  • 3,463
8 votes
3 answers
222 views

Is there a performance gain by handling data with stored procedures versus feeding it into functions after retrieval?

Title sums it up. I'm reasonably well off with PHP, and comfortable getting it to do what I need it to with values pulled from MySQL, however in the interest of expanding my knowledge I've been ...
Kaji's user avatar
  • 937
13 votes
1 answer
1k views

SQL Server - How are data pages stored when using a clustered index

I recently heard that the data pages in a clustered index aren't stored contiguously. Is this true? Perhaps data pages are normally stored contiguously with some exceptions to the rule? Or perhaps I ...
Peanut's user avatar
  • 233
5 votes
1 answer
102 views

Can I activate PITR after the DB has been used

My Postgres-Server is running for quite a while and contains probably 4-5 GB of data. Backups are done using dumps, and this works ok. Though not most efficient, it just works. Due to future growth ...
Sebastian Roth's user avatar
109 votes
5 answers
33k views

Storing vs calculating aggregate values

Are there any guidelines or rules of thumb to determine when to store aggregate values and when to calculate them on the fly? For example, suppose I have widgets which users can rate (see schema ...
BenV's user avatar
  • 4,883
31 votes
3 answers
9k views

Character vs Integer primary keys

I'm designing a database with multiple lookup tables containing possible attributes of the main entities. I'm thinking of using a 4 or 5-character key to identify these lookup values rather than an ...
BenV's user avatar
  • 4,883
18 votes
8 answers
23k views

Must-read Books for DBA [closed]

This question is almost mandatory in any SE site for basic reference. Please post only books with permanently value for DBAs in general. The post should be a must read book, the classical ones, the ...
8 votes
3 answers
876 views

Which databases are recommended to be used as embedded databases?

Which databases are recommended to be used as embedded databases to store data within an application? The embedded database may or may not synchronize back to a larger system database.
SchwartzE's user avatar
  • 339
21 votes
13 answers
1k views

The Value of Certifications [closed]

Questions What certifications do you have? Has your certification (or lack of one) ever worked for or against you? Do you intend to reach out for certification? Do you renew your certifications? If ...
Riedsio's user avatar
  • 1,377
6 votes
4 answers
3k views

Is there a way to measure replication lag in MySQL with a resolution less than 1 second?

Is there a way by which you can measure replication lag in MySQL with a resolution of less than 1 second? That is, can replication lag be measured on the microsecond or millisecond level?
Riedsio's user avatar
  • 1,377
24 votes
2 answers
3k views

Do I need separate indexes for each type of query, or will one multi-column index work?

I somewhat know the answer to this question already, but I always feel as though there is more I need to pick up on the topic. My basic understanding is that generally speaking, a single index that ...
Andrew Barber's user avatar
4 votes
4 answers
724 views

how did you become a DBA? [closed]

maybe this is more of a wiki type question, but I'd like to learn more about the (no doubt many) paths taken to become a DBA. What path lead you to become a DBA?
Ramy's user avatar
  • 191

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