Questions tagged [compression]

The name given to the process of encoding data such that it uses lesser number of bits as compared to the original representation.

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13
votes
2answers
966 views

Does there exist a way to determine the exact file that contains an allocation unit in a filegroup of multiple files?

I was hoping to get a granular view of which database files contained which allocation units for the various HoBTs (both aligned and non-aligned) living in a database. The query I've always used (see ...
2
votes
1answer
435 views

sparse column or DATA_COMPRESSION?

in one of my databases I have the following table: CREATE TABLE [app].[applicantSkill]( [ApplicantSkillID] [int] IDENTITY(1,1) NOT NULL, [applicantID] [int] NOT NULL, [skillID] [tinyint] ...
6
votes
1answer
1k views

IO request time and less write latency

I am facing issues related to constantly growing log file due to which I am getting error. When I checked SQL Log I found below messages (error log is filled of these messages almost 90%) SQL ...
22
votes
4answers
9k views

Is data retrieved from SQL Server compressed for transmission?

Is data retrieved from Microsoft SQL Server compressed? If this is controlled by the connection string, is there any simple way to tell if any particular app is using it? I'm examining analysis tools,...
15
votes
2answers
11k views

Alternative way to compress NVARCHAR(MAX)?

I am trying to compress some tables that have NVARCHAR(MAX) fields. Unfortunately, the row and the page compression do not have the desire impact (only ~100/200 MB saved for 20 GB table). Also, I am ...
14
votes
1answer
2k views

Do SQL Server compressed indexes remain compressed on rebuild without specifying data compression?

After one rebuilds their SQL Server indexes using page compression (ALTER INDEX IX1 REBUILD PARTITION = ALL WITH (DATA_COMPRESSION = PAGE)), do subsequent rebuilds (as done by some maintenance scripts ...
14
votes
2answers
1k views

Compression on a heap

The follow is a paragraph from Microsoft Docs: New pages allocated in a heap as part of DML operations will not use PAGE compression until the heap is rebuilt. Rebuild the heap by removing and ...
10
votes
2answers
8k views

Please explain the difference between row and page compression

I'm trying to determine which to apply and when is the appropriate time to apply compression. I'm posting this question to get insight from this community. I have read several articles, but wanted to ...
10
votes
1answer
1k views

What is the row overhead when using Page Compression?

I have created a table with 650 Numeric(19,4) columns. When I switch on Page Compression, by running ALTER TABLE fct.MyTable REBUILD WITH (DATA_COMPRESSION = PAGE); I get Msg 1975, Level 16, ...
8
votes
2answers
3k views

How can I see if the data in a SQL Server table is page-compressed?

This is a follow-on question to a question which I asked yesterday: Can I bulk insert into an empty page-compressed table and get full compression? The answer to that question (paraphrased from Randi ...
7
votes
2answers
793 views

Can I bulk insert into an empty page-compressed table and get full compression?

I have a lot of large tables (around 10 million wide rows) which need to be regularly loaded into SQL Server 2016 for read-only reporting. I would like these tables to be as small as possible on disk, ...
8
votes
2answers
1k views

SQL Server 2014 compression and maximum row size

I need to create wide denormalized table with lot of decimal(26,8) columns (fewer than 1024 column limit, most of the columns would be null or zero). I know about 8060 bytes per row limitation, so i ...
6
votes
2answers
2k views

TokuDB optimize table does not reclaim disk space

Was running an optimize table command against one of my tables about 11Gig in size, surprisingly used disk space grew by 2Gig immediately after optimization process finished. I would expect the ...
3
votes
0answers
1k views

Understanding how sys.dm_exec_requests represents queries being rolled back

I'm not sure whether this was an actual problem or just a normal situation where I needed to wait for rollback to finish. In either case, some insight would be appreciated. Background details I ...
3
votes
1answer
82 views

Moving Clustered Index to new filegroup results in excessive filegrowth

I've Moved the clustered index on large tables to new filegroups to defrag, compress, and to recover space more easily from the original "primary" filegroup. Problem: A 315GB compressed Clustered ...
3
votes
2answers
4k views

Does adding page compression to a table also compress existing indexes?

I am creating a series of new tables that will have page level compression enabled. Will this affect the indexes as well, or will I have to also specify compression when creating the indexes? create ...
2
votes
1answer
960 views

Does Windows Server File Compression slow Oracle DB performance?

I'm starting a new a new contract and I get to troubleshoot their Oracle instance... I'm more apps and sql, but I'll be trying to figure out their crashes and slow performance. Go figure. I can ...