SQL/MX 2.x Installation and Management Guide (G06.24+, H06.03+)

Measuring Performance
HP NonStop SQL/MX Installation and Management Guide—523723-004
15-10
SQL/MX Measurement Models
always be the same or greater than RECORDS-USED. The ratio between
RECORDS-USED/RECORDS-ACCESSED is the selectivity of the statement.
A query is most efficient when the number of records used is the same or slightly
lower than the number of records accessed. If the number of records accessed is
much larger than the number used, the query is accessing many unnecessary
rows. You can create an index to improve the selectivity.
•
DISK-READS stores the number of physical disk reads performed on the file.
•
LOCK-WAITS stores the number of times a call to the disk process waited on
locked data.
•
ESCALATIONS stores the number of times a record lock was escalated to a file
(table) lock.
•
READS stores the number of fetches.
•
WRITES stores the number of inserts.
•
UPDATES stores the number of updates.
•
DELETES stores the number of deletes.