Databases Reference
In-Depth Information
Insert:
At this time, the cost of an insert operation:
•
Count of host-controller communications
(D
s
)
for sending stream: 1
•
Cost of searching for the destination disk to insert the data
-
Count of controller-controller communications
(D
c
)
for traversing
index:
-
Count of disk accesses
(D
c
)
for traversing index:
H
•
Cost of taking logs
-
Count of controller-controller communications
(D
s
)
for sending log: 1
-
Count of disk accesses
(D
s
)
for writing log: 1
-
Count of controller-controller communications
(D
c
)
for sending ack: 1
•
Cost of inserting a stream
-
Count of disk accesses
(D
s
)
for writing stream: 1
-
Count of disk accesses
(D
c
)
for updating directory: 1
-
Count of host-controller communications
(D
c
)
for sending ack: 1
•
Cost of backup
-
Count of controller-controller communications
(D
s
)
for sending log: 1
-
Count of disk accesses
(D
s
)
for reading and writing log: 2
-
Count of disk accesses
(D
c
)
for reading and writing directory: 2
From the above, we can derive cost formulae for the response times for an insert
operation with synchronous backup, asynchronous backup, and index-cached
asynchronous backup:
