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Questions tagged [tuning]

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Why my postgresql perfomance getting worse after changing default parametes

I changed my postgresql server parameters to tune it for a query but I get worse result than default settings.Here is my changed parameters and explain result: # pgTune suggested settings ...
mahdi's user avatar
  • 1
0 votes
1 answer
74 views

How does different forms of EXISTS() affect performance in MS Sql Server?

I've been told that when checking for the existence of a row in a table, this will work: EXISTS(SELECT 1 FROM....) but that a "better" way in regards to speed performance of the query would ...
Gharbad The Weak's user avatar
0 votes
1 answer
886 views

How to use UNNEST hint in Oracle Database?

I have encountered Bug 34044661 - Poor Performance Due to SQL Not Unnesting in Oracle 19C (Doc ID 34044661.8). Oracle provides some workarounds: use UNNEST hint or alter session set "...
Astora's user avatar
  • 723
1 vote
1 answer
57 views

Explain plan not showing most columns

I am running an explain plan for a query and it only returns the following columns: explain plan for SELECT .... SET LINESIZE 130 SET PAGESIZE 0 SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY); Plan hash ...
Astora's user avatar
  • 723
3 votes
1 answer
588 views

Index usage Brent Ozar script

I'm using sp_blitzIndex to check the health of my database indexation, but I don't understand every column used in the output. I'm talking specifically about "Usage Stats" and "Op Stats&...
dba_maroc's user avatar
8 votes
1 answer
8k views

How do you tune innodb_read_io_threads?

The default value of innodb_read_io_threads and innodb_write_io_threads is 4. How do you check if your server load needs a higher number of threads? As I regularly check show engine innodb status \G, ...
Googlebot's user avatar
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0 votes
1 answer
385 views

Postgres SELECT query produces exact same explain analyze results but different execution times in the results

I have a SELECT query which when running produces the exact same plan in terms of indexes being used when doing an explain analyze however the duration of the run is different (2 seconds vs 30 seconds ...
rdbmsNoob's user avatar
  • 459
1 vote
2 answers
57 views

A SQL query optimzation issue with ORDER BY

An SQL query optimzation issue with ORDER BY Current status I have a database of Chess games and their corresponding moves (stored as strings called fens). I have two main tables 'Game' and '...
Oddbjørn Sjøgren's user avatar
0 votes
1 answer
64 views

does using optimizer_mode=first_rows_n for application that using Oracle database is a best practice?

So I'm working in application that involving display of data in table/grid. And the grid will invoke paging query to oracle. So does by tuning my application to get the best query cost with ...
Gusti Andika's user avatar
0 votes
1 answer
3k views

How to find historical sql_id executed by users

I'm trying to find historical sql_id executed by users within interval between snapshot_id from AWR. I'm using the view DBA_HIST_ACTIVE_SESS_HISTORY,DBA_USERS and DBA_HIST_SNAPSHOTS to try find the ...
Astora's user avatar
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1 vote
2 answers
562 views

Tuning MySQL on GROUP REPLICATION

I'm close to switch from old version of MySQL 5.6 ( master / slave configuration ) to MySQL 8 ( 3 nodes on multi-master configuration ) in GROUP REPLICATION. The tables are 99% InnoDB. The webfarm ...
Jung's user avatar
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0 votes
1 answer
60 views

Oracle shrink space release space to operational system in one step?

Does oracle release space to operational system when is issued alter table ... shrink space (one step) or just after move HWM (two steps) alter table ... shrink space compact?
Astora's user avatar
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1 vote
1 answer
40 views

Best way to know if my environment has workload repository license

Usually, when I need to use something that use some resource from awr, I look for LAST_USAGE_DATE at dba_feature_usage_statistics with feature name Automatic Workload Repository, but I'm almost sure ...
Astora's user avatar
  • 723
0 votes
1 answer
981 views

How to get the SQL_ID that is blocking another SQL?

Well, I'm personalizing a useful script that I found and I need put in this script what is the sql_id of the SQL that is blocking another SQL. Here is my script, if you try this, You never will get ...
Astora's user avatar
  • 723
3 votes
1 answer
123 views

Save CPU cycles on SQL Server Query Plans (Better without Stats than with on wide tables)

Assume that a query in question has a very wide set of columns. The query looks like the following: set statistics io,time on; Select a.Col1, a.Col2, b.Col3, b.Col4, c.Col5 From FirstWideTable a ...
Jamie's user avatar
  • 141
-1 votes
1 answer
557 views

How to know needed UNDO_RETENTION for a specified query of long duration? [closed]

I'd like to know whether there is some way to know the undo_retention needed for a specified query with long duration that need keep the consistence. In other words, I'd like to know how long my ...
Astora's user avatar
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0 votes
1 answer
581 views

tuned lacks oracle profile. How could I switch to it?

I'm trying to configure tuned using this tutorial And following it I'm trying to switch to oracle profile: # tuned-adm profile oracle Invalid profile. Use 'tuned-adm list' to get all available ...
Gryu's user avatar
  • 285
4 votes
2 answers
2k views

Which Plan is Better? WHERE EXISTS Instead of INNER JOIN

Did a switch to a WHERE EXISTS in temp table (Object13 in the plans) from an INNER JOIN to said temp table in final select in procedure. Logical reads plummeted, but plan cost and memory ...
BBaggins's user avatar
1 vote
2 answers
823 views

oracle slow query with diferent user [closed]

I have a question with an oracle query that takes almost 20 minutes when it is executed from a schema and yet when it runs as sys users it runs in 1 second maximum ... how is this possible? ... I do ...
miguel ramires's user avatar
0 votes
1 answer
231 views

Oracle 9i historical long queries since instance startup

please I would like to know any query that shows the queries or the top 10 queries that take more time to finish since the beginning of the instance with user and the sql sentence, I have seen several ...
Arnaldo Raxach's user avatar
2 votes
1 answer
8k views

Timeout expired error. Is it because of a query or server settings?

I am getting SQL Server timeout error in my production server, every hour (~ for 5 minutes or more) during night time. This SQL server database is supporting a .NET application. I have scheduled an ...
sparktech's user avatar
  • 157
1 vote
0 answers
274 views

Improve qps for postgres write

I am trying to improve the performance of my postgres instance in aws. I am using aws rds db.t2.large Here is my table structure CREATE TABLE public.my_test ( test_index1 text COLLATE ...
J L's user avatar
  • 59
4 votes
1 answer
11k views

How do you monitor slow query in AWS RDS Postgres

My RDS Postgres has 5 read replica and it's the maximum number of read replica and cannot scale out by increasing read replica. In this situation, some of the read replicas occur too much high CPU ...
user avatar
2 votes
1 answer
576 views

sp_BlitzIndex -- 'High value" vs 'High Impact' [closed]

Sorry, I may be missing something super-obvious here, but I've googled this and asked some colleagues and am not finding a satisfactory answer. I've been using sp_BlitzIndex for a few months now ...
Robert H's user avatar
1 vote
3 answers
70 views

Optimize SQL query in form of a Procedure

I have a Oracle SQL query with multiple "IN" statements. It takes around a minute to execute in an average. My task is to optimize this query in form of PL/SQL procedure so that the user gets the ...
Snehil Kandpal's user avatar
2 votes
1 answer
709 views

Effect of over allocating shared_buffers

I have a 9.6 PostgreSQL RDS instance that I am tending to, but did not initially configure, and have been struggling with two different symptoms: the system (a db.r3.2xlarge w/ 61GB memory) would ...
bimsapi's user avatar
  • 121
2 votes
1 answer
189 views

Ideas how to make this query faster?

I have the following query: SELECT TabPohybyZbozi.ID, TabPohybyZbozi.NazevSozNa2, TabZakazka.Nazev, TabDokladyZbozi.DatPorizeni, TabPohybyZbozi.IDDoklad FROM ...
jericzech's user avatar
  • 945
0 votes
1 answer
295 views

Database Engine Tuning Advisor

I analysed a huge query in DTA. The database is kind of badly designed and does not have primary keys on tables, also they dont have clustered indexes on them. I found around 80 tables as such. Now, ...
rohit's user avatar
  • 3
11 votes
2 answers
25k views

Sql Server, Is "Reorganize Files Before Releasing Unused Space" better or worse?

I could not find a satisfactory answer. I fully understand that "Shrink" will cause index defragmentation, and that can worsen performance. But, is not this option to reduce defragmentation? So, to ...
Diego Soto's user avatar
2 votes
1 answer
2k views

Table valued function VS Stored procedure

There's a function that : returns only 1 row has only 1 parameter has multiple joins on different tables, each only to return a single scalar value is called only once at each login of a web ...
A_V's user avatar
  • 1,364
2 votes
1 answer
626 views

PostgreSQL 9.6.2 perfomance

I need help for server side optimization. I think it is a system file cache problem but I'm not sure, maybe I am wrong. I have 2 servers (S1, S2) with PostgreSQL 9.6.2 on both of them, the database ...
suquant's user avatar
  • 121
0 votes
1 answer
3k views

Pt-query-digest date ranges do not work as expected

Analyse Queries with Pt-query-digest I am using pt-query-digest to analyse queries and would like to analyse a specific time range only, in order to measure the effect of adding new indices and ...
Stefan's user avatar
  • 221
1 vote
1 answer
249 views

Should I ever use query hints?

SQL Server 2008 R2, Dynamics AX 2009 We have this ugly query DECLARE @P1 NVARCHAR(5), @P2 INT, @P3 INT, @P4 NVARCHAR(11), @P5 INT, @P6 NVARCHAR(5), @P7 NVARCHAR(11)SELECT A.SALESID, A.LINENUM, ...
George K's user avatar
  • 2,296
3 votes
2 answers
4k views

TSQL Execution Plan - Estimated Number of Rows = 1 - Poor Performing Query

TSQL MSSQL 2008r2 I am trying to tune a poor performing query. For 3 out of 4 of the largest tables (several millions of rows) being queried (index seeks), the plan has decided that the estimated ...
Mazhar's user avatar
  • 793
1 vote
1 answer
5k views

How to get MariaDB (MySql) query time?

I'm using MariaDB 10.1. How to get actual query time for all of executed query? It seems that SHOW PROFILES; was deprecated. Is there a better solution for database tuning? Edit: It's deprecated only ...
x01saa's user avatar
  • 162
1 vote
1 answer
12k views

Performance tuning large mysql databases for zabbix

I have been working on tuning a mysql database for zabbix for quite some time now. We do not actually have a DBA to assist with this. We have a Zabbix server running 16k values per second. Our ...
Som3guy's user avatar
  • 75
0 votes
1 answer
5k views

How to solve log file sync wait in oracle 12c

I have performance issue with Oracle instance. There is some java process that makes massive inserting into database. And the top wait event is "log file sync". I tried to change some Oracle database ...
whitebeast's user avatar
1 vote
0 answers
232 views

Operating system tuning for PostgreSQL

I'm working at the pgconfig.org[1] tool. PgConfig it's a tool for suggest a tuning configuration for a PostgreSQL environment. I'm finding some disk tuning documentations to implement a suggestion ...
Sebastian Webber's user avatar
7 votes
4 answers
4k views

Hash Match inner join in simple query with in statement

I am running the execution plan for the following query: select m_uid from EmpTaxAudit where clientid = 91682 and empuid = 42100176452603 and newvalue in('Deleted','DB-Deleted','Added') Here is ...
Adolfo Perez's user avatar
0 votes
1 answer
55 views

Is there a way to compare very short periods of activity in Oracle?

I am having a problem with an application that requires very low latency (less than 100 ms per txn.) Every once in a while we will see spikes where transactions take 20-30 SECONDS. We looked at the ...
GregH's user avatar
  • 279
0 votes
1 answer
843 views

Same query same data different server different query plan

I have a query that hits a view, which references other views etc...several levels down. The query plan is a bit complex. I run the query on 2 different servers. On both servers, the number of rows ...
Steve Rauda's user avatar
3 votes
1 answer
170 views

Sort operation SQL Server 2012

I am trying to optimize a query and the sort operation (91% cost) is the costliest operation. Any help will be appreciated. Query is : SELECT TOP 1 ArchiveType, CONVERT(NVARCHAR(30), A....
Viv's user avatar
  • 31
6 votes
1 answer
123 views

Query tuning issues

I'm in trouble trying to tune this following query. I used to be 100% focused in the infrastructure side of the stuff, but since August this year I'm working for a processing card company that is ...
Marcelo Moraes's user avatar
0 votes
1 answer
42 views

Query speed improvements [closed]

Referencing: CREATE TABLE words ( word_id int(11) NOT NULL, word varchar(25) NOT NULL, PRIMARY KEY (word) ) CREATE TABLE synonyms ( source_index int(10) unsigned NOT NULL, ...
user1919695's user avatar
1 vote
2 answers
5k views

Please recommend changes for my.cnf

I am not having any performance problems per se but want to improve my sites' performance if possible. Would appreciate any advice for how I can improve my.cnf. I have just one server, not ...
Amin Sabet's user avatar
3 votes
3 answers
3k views

Export Query Plans

I know it is very easy to export a single query plan. My question is, when I create a query which returns multiple plans, such as looking at the most costly queries on the server, is there a way to ...
pshore73's user avatar
  • 427
4 votes
2 answers
8k views

Database Tuning Issues

I'm not a DBA so looking for some advice on tuning a MySQL (MyISAM) database. I've found that during peak hours we are getting pretty severe load spikes which are slowing down the web front-end. I've ...
Stephen91's user avatar
  • 113
0 votes
1 answer
1k views

Confused over table_open_cache

I've been reading about the table_open_cache and I'm slightly confused about how big it should be, I've seen conflicting advice. My DB is running on MyISAM and has 199 tables. I ran into an issue ...
Stephen91's user avatar
  • 113
1 vote
1 answer
2k views

Why the optimizer does not use an Index Unique Scan?

I am on Oracle 10.2.0.4.0. I have a big Index Organized Table (IOT) with 74 columns and over 345 million of rows. An external tool execute a batch where I cannot touch the source code. The critical ...
Shaunyl's user avatar
  • 528
6 votes
2 answers
2k views

Backup tuning for large databases

I am tuning SQL Server backups using compression, writing to multiple files, and changing the BufferCount and MaxTransferSize options. I have a SQL Server instance with a 4 TB database and several ...
Dave M.'s user avatar
  • 103