I got some problems with my SQL Server. Some external queries write into the Temp db and every 2-3 days it is full and we have to restart the SQL database. I got who is active on it. And also we can check monitor it over grafana. So I get a exact time when the query starts to write a lot of data into the temp db. Can someone give me a tip on how I can search for the user when I get the exact time?
select top 40 User_Account, start_date, tempdb_allocations
from Whoisactive
order by tempdb_allocation, desc
where start_date between ('15-02-2023 14:12:14.13' and '15-02-2023 15:12:14.13')
User_Account
Start_Date
tempdb_allocations
kkarla1
15-02-2023 14:12:14.13
12
bbert2
11-02-2023 12:12:14.13
0
ubert5
15-02-2023 15:12:14.13
888889
I would add this as a comment but I don’t have the necessary reputation points.
At any rate - you might find this helpful.
https://dba.stackexchange.com/questions/182596/temp-tables-in-tempdb-are-not-cleaned-up-by-the-system
It isn’t without its own drawbacks but I think that if the alternative is restarting the server every 2 or 3 days this may be good enough.
It might also be helpful if you add some more details about the jobs that are blowing up your tempdb.
Is this problematic job calling your database once a day? Once a minute? More?
I ask because if it’s more like once a day then I think the answer in the link is more likely to be helpful.
Related
We have a bunch of devices in the field (various customer sites) that "call home" at regular intervals, configurable at the device but defaulting to 4 hours.
I have a view in SQL Server that displays the following information in descending chronological order:
DeviceInstanceId uniqueidentifier not null
AccountId int not null
CheckinTimestamp datetimeoffset(7) not null
SoftwareVersion string not null
Each time the device checks in, it will report its id and current software version which we store in a SQL Server db.
Some of these devices are in places with flaky network connectivity, which obviously prevents them from operating properly. There are also a bunch in datacenters where administrators regularly forget about it and change firewall/ proxy settings, accidentally preventing outbound communication for the device. We need to proactively identify this bad connectivity so we can start investigating the issue before finding out from an unhappy customer... because even if the problem is 99% certainly on their end, they tend to feel (and as far as we are concerned, correctly) that we should know about it and be bringing it to their attention rather than vice-versa.
I am trying to come up with a way to query all distinct DeviceInstanceId that have currently not checked in for a period of 150% their normal check-in interval. For example, let's say device 87C92D22-6C31-4091-8985-AA6877AD9B40 has, for the last 1000 checkins, checked in every 4 hours or so (give or take a few seconds)... but the last time it checked in was just a little over 6 hours ago now. This is information I would like to highlight for immediate review, along with device E117C276-9DF8-431F-A1D2-7EB7812A8350 which normally checks in every 2 hours, but it's been a little over 3 hours since the last check-in.
It seems relatively straightforward to brute-force this, looping through all the devices, examining the average interval between check-ins, seeing what the last check-in was, comparing that to current time, etc... but there's thousands of these, and the device count grows larger every day. I need an efficient query to quickly generate this list of uncommunicative devices at least every hour... I just can't picture how to write that query.
Can someone help me with this? Maybe point me in the right direction? Thanks.
I am trying to come up with a way to query all distinct DeviceInstanceId that have currently not checked in for a period of 150% their normal check-in interval.
I think you can do:
select *
from (select DeviceInstanceId,
datediff(second, min(CheckinTimestamp), max(CheckinTimestamp)) / nullif(count(*) - 1, 0) as avg_secs,
max(CheckinTimestamp) as max_CheckinTimestamp
from t
group by DeviceInstanceId
) t
where max_CheckinTimestamp < dateadd(second, - avg_secs * 1.5, getdate());
I'm using oracle db. I want to be able to count the number of times that a SQL statement was executed in X hours. For instance, how many times has the statement Select * From ExampleTable been executed in the past 5 hours?
I tried looking in V$SQL, V$SQLSTATS, V$SQLAREA, but they only keep a record of a statement's total amount of executions. They don't store what times the individual executions occurred. Is there any view I missed, or something else that does keep track of each individual statement execution + timestamp so that I can query by which have occurred X hours ago? Thanks for the help.
The views in the Active Workload Repository store historical SQL execution information, specifically the view DBA_HIST_SQLSTAT.
The view is not perfect; it contains a summary of the top SQL statements. This is almost perfect information for performance tuning - in practice, sampling will catch any performance problem. But if you're looking for a perfect record of every SQL execution, as far as I know the only way to get that information is through tracing, which is buggy and slow.
Hopefully this query is good enough:
select begin_interval_time, end_interval_time, executions_delta, dba_hist_sqlstat.*
from dba_hist_sqlstat
join dba_hist_snapshot
on dba_hist_sqlstat.snap_id = dba_hist_snapshot.snap_id
and dba_hist_sqlstat.instance_number = dba_hist_snapshot.instance_number
order by begin_interval_time desc, sql_id;
Apologies for putting this in an answer instead of a comment (I don't have the required reputation), but I think you may be out of luck. Here is an AskTOM asking basically the same question: AskTOM. Tom says unless you are using ASH that just isn't something the database is designed to do.
I have some queries that run every day for several month with no problem. I didn't change anything in the queries for a long while.
In the past few days some of them fail. Error message says something regarding some fields: "Field 'myfield' not found.". these queries usually involve some sub-queries and window functions.
Example for the BQ guys:
On 2015-08-03 Job ID: job_EUWyK5DIFSxJxGAEC4En2Q_hNO8 run successfully
on the following days, same query, failed. Job IDs: (job_A9KYJLbQJQvHjh1g7Fc0Abd2qsc , job__15ff66aYseR-YjYnPqWmSJ30N8)
In addition, for some other queries running times extended from minutes to hours and sometime return "timeout".
My questions:
Was something changed in the BQ engine?
What should I do to make my queries run again?
Thanks
So the problem could be two folded:
An update to query execution engine was rolled out during the week of August 3, 2015 as documented in the announcement
If this is the case, you need to update your queries.
Some performance issues were detected lately, but in order to actually identify if there is something wrong with your project or not, you need to create a issue request I did the same in past and it was fixed.
I would like to optimise a mapping developped by one of my colleague and where the "loading part" (in a flat file) is really really slow - 12 row per sec
Currently, to get to the point where I start writting in my file, I take about 2 hours, so I would like to know where I should start looking first otherwise, I will need at least 2 hours between each improvment - which is not really efficient.
Ok, so to describe simply what is done :
Oracle table (with big query inside - takes about 2 hours to get a result)
SQ
2 LKup on ref table (should not be heavy)
update strategy
1 transformer
2 Lk up (on big table - that should be one optimum point I guess : change them to joiner)
6 stored procedure (these also seem a bit heavy, what do you think ?)
another tranformer
load in the flat file
Can you confirm that either the LK up or the stored procedur part could be the reason why it is so slow ?
Do you think that I should look somewhere else to optimize ? I was thinking may be only 1 transformer.
First check the logs carefuly. Look at the timestamps. It should give you initial idea what part causes delay.
Lookups to big tables are not recommended. Joiners are a better way, but they still need to cache data. Can you limit the data for cache, perhaps? It'll be very hard to advise without seeing it.
Which leads us to the Stored Procedures: it's simply impossible to tell anything about them just like that.
So: first collect the stats and do log analysis. Next, read some tuning guides on the Net - there's plenty. Here's a more comprehensive one, but well... large - so you might like to try and look for some other ones.
Powercenter Performance Tuning Guide
This is a 4 part question
What is the logic behind SQL_ID. . . Does the value change for the same SQL over time? Does it persists between DB Restarts? Or every plan change gives a new SQL_ID?
How can i check the plan change history for a particular query? Given the SQL_ID i tried querying dba_hist_sqlstat table but it does not give the time of plan change and other details so as to be able to match with the v$sql_plan table.
I have the parameter optimizer_mode set to FIRST_ROWS. Even then when is see the table dba_hist_sqlstat, it indicate ALL_ROWS for some SQL_IDs . . . Can oracle disregard the instance level parameter to use what it deems most suitable?
Between 8PM and 2 PM a query was performing badly. Taking 6 seconds for its execution. After 3 PM the query started responding in < 1 Second. I have the AWR report for the periods that shows this detail. There was no difference in load on the DB in these 2 periods. How could i arrive at the root of this? I am trying to find the History of the plan change but appreciate more feedback to best analyze such issues.
The DB Version is Oracle 10.1.0.4 running on AIX 5.3 64b
1.- SQLID is calculated with a hash function based on the actual SQL text, it shouldnt change with restart or between databases at least the same versions, different oracle versions could have different hashing functions right?, so as long as you do not change the sql text (this includes blanks commas and everything) SQLID will remain the same.
2.- Use DBMS_XPLAN.DISPLAY_AWR to display all plans for a SQL_ID: select * from table(dbms_xplan.display_awr(sql_id => '[your SQL_ID]'));
3.- Oracle will only do this if a query has an OPTIMIZER GOAL hint in it.
4.- There are many things in play for this one. I would start by looking at top 5 timed events in AWR for both periods of time. If they are alike, I would then go investigate the PLAN history for the statement, see if it changed during periods and how data behaved during the periods as well. One of these three should give you the answer.