MC Which statement is NOT CORRECT? RAID level 5 strikes a balance between read and write performance, storage efficiency, and fault tolerance. incorrect Block level striping as used in RAID 0 does not increase read performance. correct To store the same amount of data, RAID 1 needs twice the amount of storage capacity compared to RAID 0. incorrect RAID level 0 is used if performance is more important than fault tolerance. incorrect
MC Which statement is NOT CORRECT? The management of data storage is more expensive than the purchase of storage hardware, which is why businesses opt for enterprise storage subsystems. incorrect 'Network attach' refers to establishing a many-to-many connection between storage devices and the corresponding servers by means of network technology. incorrect Although SCSI has been a popular medium for connecting storage devices to servers and/or processors in the past, nowadays, it is not used anymore for high performance and high capacity workstations and servers. correct The SCSI I/O command set is a type of block-level I/O protocol which can be exchanged over SCSI, Ethernet or Fibre Channel cabling. incorrect
MC Which statement is NOT CORRECT? A DAS does not offer out-of-the-box capabilities for centralized storage management and sharing unused disk capacity across servers. incorrect A NAS gateway receives file level I/O requests from servers connected to the LAN or WAN and translates these into SCSI block I/O commands to access the external storage devices - this latter connection can be organized by DAS or SAN technology. incorrect Compared to SAN, a NAS is much less expensive and much simpler in soft- and hardware. However, it achieves performance similar to a NAS set-up. correct A SAN is typically best in terms of performance, because it often uses Fibre Channel, the LAN network is freed from storage related traffic, and Fibre Channel compatible storage devices have some onboard intelligence, which allows them to perform certain tasks autonomously, e.g. server-free back-ups. incorrect
MC Which statement is NOT CORRECT? Table cardinality is another way of referring to the number of columns in a table. correct The number of block accesses determines the performance, not the number of rows retrieved. incorrect An index can be used to create a physical ordering of rows. incorrect A SAN is typically best in terms of performance, because it often uses Fibre Channel, the LAN network is freed from storage related traffic, and Fibre Channel compatible storage devices have some onboard intelligence, which allows them to perform certain tasks autonomously, e.g. server-free back-ups. incorrect
MC Which statement is NOT CORRECT? 'Network attach' refers to establishing a many-to-many connection between storage devices and the corresponding servers by means of network technology. incorrect Current versions of SQL do not impose any standardization on the internal data model nor on the way in which a relational data model is implemented physically. incorrect Current versions of SQL require a specific internal data model. correct A SAN is typically best in terms of performance, because it often uses Fibre Channel, the LAN network is freed from storage related traffic, and Fibre Channel compatible storage devices have some onboard intelligence, which allows them to perform certain tasks autonomously, e.g. server-free back-ups. incorrect
MC Which statement is NOT CORRECT? An index can be used to create a physical ordering of rows. incorrect Compared to SAN, a NAS is much less expensive and much simpler in soft- and hardware. However, it achieves performance similar to a NAS set-up. correct Rolling upgrades are an example of how to avoid downtime in a cluster computing set-up. incorrect For range queries, a primary or clustered index is more efficient than a secondary index. incorrect
MC Which statement is CORRECT? Table cardinality is another way of referring to the number of columns in a table. incorrect If no further statistical information about a predicate is available, the filter factor of that predicate can be estimated by dividing 1 by the number of different values the attribute type can have. correct The filter factor of a predicate is the fraction of rows that contain a missing value for that predicate. incorrect SQL is a declarative language, meaning that the programmer has to specify what data to retrieve and how the data is to be located and retrieved from the physical database files. incorrect
MC Which statement is NOT CORRECT? For range queries, a primary or clustered index is more efficient than a secondary index. incorrect The more selective a query predicate's FF, the less desirable it is to use the index on the corresponding attribute type in the access plan. correct The number of block accesses determines the performance, not the number of rows retrieved. incorrect The more attribute types are included in the index, the higher the performance impact is on update queries. incorrect
MC Given 2 tables R and S. Which of the following join strategies is described by the following algorithm:
denote S -> outer table
for every row s in S do {
for every row r in R do {
if r(a) = s(b) then join r with s and place in output buffer
}
} Hash join incorrect Sort-Merge join incorrect None of these joins incorrect Nested loop join correct
MC Given 2 tables R and S. Which of the following join strategies is described by the following algorithm:
Stage 1:
sort R according to r(a)
sort S according to s(b)
Stage 2:
retrieve the first row r of R
retrieve the first row s of S
for every row r in R do {
while s(b) < r(a) do {
read the newt row s of S
if r(a) = s(b) then join r with s and place in output buffer
}
} None of these join strategies incorrect Sort-Merge join correct Hash join incorrect Nested loop join incorrect