brotherhood_of_LAN - 10:51 am on Jan 8, 2013 (gmt 0)
MySQL I assume
It really depends on how interested you are on the MySQL internals InnoDB Page Structure [dev.mysql.com]
The standard engine used in recent MySQL releases is InnoDB, which clusters your data on a primary key. The first n bytes of data are put on a page alongside the primary key, so a lookup by primary key is very fast as is the row retrieval.
This data may end up in the buffer pool https://dev.mysql.com/doc/refman/5.5/en/innodb-buffer-pool.html if it is continually accessed. I believe the default is up to 768 bytes per record will go into the buffer pool.
If you have a table with large TEXT/BLOB columns, those columns will fill up the 768 byte allocation... and can potentially fill up your buffer pool. This can cause a performance issue if you have data that would be better suited to the buffer pool, like other indexes. The larger data will also have to be fetched from two separate locations because it's larger than the default allocated space.
So saying "The size of the records (too large and it goes over 2 pages)" fits this scenario. The manual and mysql blogs do a better job of explaining it.