A checkpoint marks a significant point in a transaction, when Sybase IQ writes to disk certain information it tracks internally. IQ uses this information in the event you need to recover your database.
Sybase IQ uses checkpoints differently than OLTP databases such as Adaptive Server Anywhere. OLTP databases tend to have short transactions, that affect only a small number of rows. Writing entire pages to disk would be very expensive for them. Instead, OLTP databases generally write to disk at checkpoints, and write only the changed data rows.
As discussed in Chapter 1, “Overview of Sybase IQ System Administration,” Sybase IQ is an OLAP database. A single OLAP transaction can change thousands or millions of rows of data. For this reason, Sybase IQ does not wait for a checkpoint to occur to perform physical writes. It writes updated data pages to disk after each transaction commits. For an OLAP database, writing full pages of data to disk is much more effective than writing small amounts of data at arbitrary checkpoints.
