Questions tagged [data-pages]

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16
votes
1answer
11k views

How do I decompose ctid into page and row numbers?

Each row in a table has a system column ctid of type tid that represents the physical location of the row: create table t(id serial); insert into t default values; insert into t default values; ...
6
votes
1answer
2k views

SQL Server: How to create a table that fills one 8 KB page?

Is there a way to calculate the amount of data that fills one 8 KB page in SQL Server and create a table that fills one page entirely? This kind of table is presented in in this blog post.
13
votes
1answer
1k views

Slot Array and Total Page Size

I continue to read in many forums and on many blogs that a page is comprised as shown below: Page Size: 16 x 512B = 8192B Page Header: = 96B Maximum In_Row Row: = 8060B This leaves (...
4
votes
1answer
241 views

Logical read count varies

In this post the writer runs a query several times. I notice the logical reads vary a little across executions. There is a difference of about 2 pages in a total of a few thousand pages read. It ...
9
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, ...
11
votes
2answers
3k views

SUM of DATALENGTHs not matching table size from sys.allocation_units

I was under the impression that if I were to sum the DATALENGTH() of all fields for all records in a table that I would get the total size of the table. Am I mistaken? SELECT SUM(DATALENGTH(Field1)) ...
3
votes
1answer
5k views

DB2: Is it good to create the index table space to use 32 KB data page

I found our DB2 server configs all the index into one table space. And it then defines the table space to use 32kb data page. Is this good? How to judge it? Any advice is welcome.
0
votes
2answers
232 views

What is the relation between Tablespaces, .frm & .ibd files and database pages in MySQL?

I looked in the documentation but there was not a clear answer regarding their relation, can someone give an real life example of their relation in MySQL? Database pages are smallest read write unit ...