An evaluation of whether a system works well enough to be fit for purpose. Normally performance refers to the speed with which a system completes an operation or set of operations over time.

learn more… | top users | synonyms

3
votes
1answer
170 views

Biggest wait WriteLog

I have been given a server (SQL Server 2008R2 64 bit) where our application is running. There has been a gradual decrease in the performance of the application. Now it has come to a point where ...
3
votes
0answers
196 views

Slow transactions, many locks

At high load conditions the server app stops responding to client because begin/commit statements are executing very slowly (some take 15 seconds). The queries are simple - insert, update two columns ...
3
votes
0answers
89 views

Optimizing postgres row overlap constraints involving UUIDs and GIST

For various reasons all my tables have UUIDs as primary keys and I need to exclude duplicate rows where the combination of area_id, user_id, and finished_at <-> started_at window. The only way I ...
3
votes
0answers
419 views

Do OR conditions in Oracle SQL queries spoil index use / cause full table scan?

I have a query on Oracle 11g of the following type, which results in a series of highly inefficient full table scans: select t.Id, t.ObjectId, t...[other Tasks columns] , od1...[ObjectData1 ...
3
votes
2answers
157 views

Enhance performance of update query

I have a query that is running against a table with 50 million rows. The phone number is stored as a CHAR(10) and an ETL process is changing the phone number if it has certain values. We are seeing ...
3
votes
0answers
385 views

Poor performance in my pgpool cluster

I've configured a postgres cluster with pgpool2 using the following link. The replication seems to be ok, but I ran some benchmarks (pg_bench) and the performance is lower than a single node, for ...
3
votes
0answers
1k views

How to properly monitor the number of PostgreSQL database connections?

I tried to use a Nagios script for monitoring the number of database connections on a Postgres database and I reached this problem: these are counted as currently open-connections and measured every 5 ...
3
votes
2answers
603 views

Query planner thinks doing a sequential scan on a very large table is faster than using an index?

I've got a query that selects the most favorited photo for each of the last 12 editions for a particular domain (this is just a segment of a larger query, but the problem seems to stem from here): ...
3
votes
0answers
39 views

High CPU usage on SQL server - Slow queries [duplicate]

Our MS SQL Server is using about 95% of the CPU-power. After a server (hardware) restart, or a SQL-Service restart, the usage is 0% and slowly increases over the course of 1-3 days. Depending on how ...
3
votes
0answers
2k views

Oracle high Paging Faults

What are the reasons that lead to terrible high Paging faults. The following is the topas information and background about the Environment. OS: AIX 6.1 Softwares: Oracle 11gR2 Paging Space:30720 ...
3
votes
2answers
299 views

Why is my CPU usage increase after setting database to read-only on SQL Server 2008 R2 [closed]

I administrate a reporting database. We run all the de-normalization process on a database DB1 daily, then we copy all the data to an another database DB2 on the same server which is queried by web ...
3
votes
3answers
1k views

Increase Oracle buffer cache gets slower

So we're contemplating increasing our Oracle 11gR2 buffer cache. They said they tried it in the past and things appeared to get worse - so they undid the change. They, however, have no idea why ...
3
votes
1answer
579 views

Select * from statement execute very slowly, innodb io read speed is low

I have a very simple query " select * from ap_statistic " running in my servers. the servers have the same hardware and software configuration (CPU 8 core, mem :32G, OS: redhat 5.5, mysql version: ...
2
votes
2answers
4k views

MS SQL Server 2008: How to improve performance after deleting transaction log file

Due to the size of transaction log file (it grew up to 200 GB) I had to delete it because the disk was running out of space. I know this is not a good practice but anyway after that the performance is ...
2
votes
4answers
865 views

Advice on choosing a really fast DBMS

I am working on a project that does real-time monitoring of data being transmitted, and logs if there are any of the various type of errors, etc. The CRUD operations are real-time. We initially ...
2
votes
5answers
3k views

How to determine why a MySQL server has become slow and requests sometimes time out?

I'm working on my first project that makes heavy use of a MySQL database and am struggling to understand performance issues I'm having. Most of the time, responses are returned quickly from the ...
2
votes
3answers
141 views

Performance difference between searching table with 350 columns and searching table with 25 columns

I am currently doing some hibernate performance test. My requirement is to search for data in a particular column of a table containing 8 million rows and 350 columns. Currently, I don't have the ...
2
votes
4answers
2k views

One table with many rows or many tables with a few rows

I'm having a question rounding my mind. It's better to create one table and store a lot of rows there or create various tables and have a few rows on them? What's the performance and the I/O saved at ...
2
votes
4answers
481 views

Help understanding SQL Server 2005 execution plan

One of my stored procedure has long execution time (average around 4 to 7 minutes). Now I trying to tweak it an make it run faster. I am looking at execution plan and two things I see that using ...
2
votes
3answers
801 views

SQL server disk write queue dramatically grows sometimes

I have SQL Server 2008 and a single database with full recovery model. Usually, the queue length is less than 1. But sometimes it grows up to several thousands (3000!!) for a few seconds. At this time ...
2
votes
1answer
431 views

Query takes hours

Up until now all queries in my PostgreSQL application were fast. During the last days, sometimes a query takes several hours. Index are healthy, because after dump, restore, vacuum -z, it is still the ...
2
votes
5answers
2k views

Setting up a Redundant Sql Server 2008 Configuration While Retaining High Performance and Minimal Downtime

We have a situation where we are moving to a new hosting facility and are attempting to configure our new database environment. However, none of us are formal DBA's so a lot of what we are doing is ...
2
votes
2answers
67 views

query plan caching (sql server)

Is there a measure of time frame as to which the execution plan of inline queries will cached?
2
votes
3answers
298 views

What affects the speed of a count(*) besides the number of records

I have a query like SELECT COUNT(*) FROM Foo Where Bar = 1 AND Baz = 2 the table has 12934600 records of which 1000001 match that predicate Looking at the query statistics I see (1 row(s) ...
2
votes
2answers
858 views

How can you tell when a query plan reuse is causing performance problems

When investigating a performance issue, a workmate suggested running DBCC FREEPROCCACHE to clear the plan cache. He came to this conclusion after noticing performance improved after a reboot. This ...
2
votes
2answers
2k views

How to tune mysql to be inmemory-like

I've given MySQL 5GB of memory (I use innodb), but when I insert lots of data (dumpfile is 1GB), hard drive I/O is still a bottleneck (CPU is not busy and hard drive is). Is it possible to force ...
2
votes
2answers
922 views

PostgreSQL performance degradation over time on a write intensive db

I have observed a weird situation that over time the performance of a query (a combination of queries explained below) degrades, meaning at the start of testing (for a few minutes) the time of the ...
2
votes
2answers
8k views

Most efficient way to add a serial column to a huge table

What's the fastest way to add a BIGSERIAL column to a huge table (~3 Bil. rows, ~ 174Gb)? EDIT: I want the column to be incremented values for existing rows (NOT NULL). I didn't set a fillfactor ...
2
votes
3answers
3k views

Improve `Update` performance (rows locking issue)

I am running 30 scripts (PHP CLI) on Linux , each script are updating (loop) the data in the MySQL database. When I typed 'mysqladmin proc' in terminal, I can see a lot of rows has been locked for ...
2
votes
1answer
599 views

Disk Latency vs Throughput

I've searched the web for a little while and haven't found an answer I'm confortable with. I am testing a SQL Server on a VM that was presented new disc. If disk latency is reduced, shouldn't ...
2
votes
2answers
213 views

Large number of VLF and shrinking the log

If there are lot number of VLF then it will effect the performance of the queries. I saw that solution is to shrink the log file. But shrinking the file is also bad. So how to take control of whole ...
2
votes
2answers
10k views

Splitting a large table to improve performance

This is a follow-up to an earlier question. I have a SQL Server 2008 R2 Standard server, that holds a single database, which itself has almost nothing except a large table. The table is 100+ million ...
2
votes
4answers
980 views

When do I use another type index than integer? (eg string) [integer vs string index]

I was reading about relational databases like sqlite and I always see the schema for user storage like: UserID (index) | Username | Password but wouldn't it be actually much faster to use Username ...
2
votes
4answers
1k views

Spread SQL Server data files across devices to improve performance?

Would it improve performance of a database in SQL Server if I place the .mdf (rows data) and .ldf (log) files on separate sets of raided disks, as opposed to having both files on the same set of ...
2
votes
2answers
2k views

MongoDB - Should I separate the journal and the data to different drives?

I have seen and heard from multiple sources that it can be a good idea, performance-wise, to write your db journal and your data files to separate disks. What's the recommended way to do this (e.g. ...
2
votes
3answers
14k views

which mysql version to use - 5.1 or 5.5?

I am designing a new database. There are going to be around 1000 write queries per second. There may be as much as 10000 read per second. Which MySQL version is recommended? I came across a post on ...
2
votes
2answers
625 views

Is it a good idea to move high-volume and highly-accessed tables to a separate database?

Ours is a web-based application (built on multi-tenant architecture) running PostgreSQL v9.1.3. There are about 450 tables in our application, out of which 2-3 tables, specific to a module in the ...
2
votes
3answers
33k views

SQL Server 2008 R2 High memory usage

I have SQL Server 2008 R2 that runs multiple jobs over night, the problem is SQL Server will eat up all RAM and CPU, then it will not release the RAM resources after the job finishes, as a workaround ...
2
votes
1answer
111 views

SQL Server - Data and Log Separation

We have a SQL Server 2008 R2 which has, among others, a 12K RPM HDD and a 7.2K RPM HDD. The original intention was to store the data files on the 12K drive and the log files on the 7.2K drive, as is ...
2
votes
3answers
191 views

How to make stored procedures more readable without harming performance

I come from OOP background, and I need to write and maintain huge stored procedures. Naturally, the sprocs become quite unreadable very quickly, no matter how much I try formatting, giving readable ...
2
votes
2answers
649 views

Optimize simple query using ORDER BY date and text

I have a query to a table in Postgres with an order based on a date field and a number field, this table has 1000000 records The data types of the table are: fcv_id = serial fcv_fecha_comprobante = ...
2
votes
3answers
4k views

When to periodically RESTART SQL SERVER 2008 R2? [closed]

So I've read that it's really a bad practice to restart SQL Server on a production environment.. Does restarting SQL Server speed it up? Automatically restart SQL Server 2008 Why are periodic ...
2
votes
1answer
289 views

How do you figure out what planner cost constants to use in Postgres?

I'm using Postgres 8.4 right now. Performance has started to become an issue as our tables have grown in size and our queries in complexity, so I've started to look into some performance tuning, but I ...
2
votes
2answers
4k views

Will altering order of columns in GROUP BY affect performance?

I have a SQL query like this: SELECT A, B, (CASE WHEN C=0 THEN 0 ELSE 1 END), COUNT(D) FROM SomeTable GROUP BY A, B, (CASE WHEN C=0 THEN 0 ELSE 1 END) On a huge dataset the actual execution plan ...
2
votes
2answers
1k views

Does it ever make sense to use RAM Disk to force RAM allocation for tempdb with SQL Server 2008

If I give all RAM to SQL Server, it will use it's own pattern to determine what RAM to allocate for what. If I allocate portion of RAM as RAM Disk and put tempdb into that disk it will force RAM ...
2
votes
2answers
1k views

Trying to optimize query for performance (MySQL)

So I have this table that has a lot of foreign keys but when I will a record, I need to join all on those tables because I generally need those fields for the record to make any sense. The basic ...
2
votes
1answer
581 views

Maintenance Plan Takes Too Long - Locks Tables - Indexing To Blame

System: I have a Maintenance Plan that Rebuilds Indexes for Several Tables (10 tables, 50M records total). Issue: During the Index Rebuild (~20 minutes), we fail to insert data into the DB ...
2
votes
1answer
2k views

Postgres multiple joins slow query, how to store default child record

Ive got a small database in Postgres, about 10,000 records storing company customers. I have a "slow" performing query (about half a second) which is performed very frequently, and my boss wants me to ...
2
votes
2answers
385 views

How to quantify TEMPDB usage in relation to other databases hosted on same hardware?

Working on a project to decide if configuration 1 or 2 is the best way to organise disks for my SAN: Config1 (sql 2008): 8 disks @ raid 10 data 2 disks @ raid 1 logs 2 disks @ raid 1 tempdb 2 disks ...
2
votes
3answers
441 views

Express union which is dependent on other results

I would like to make a union of two tables that are actually in a hierarchical constellation. How would I write that in relational algebra? Say table A is the parent of B in a 1:n relationship. ...