Learning Visually with Examples [Electronic resources] نسخه متنی

Uncommitted read applications acquire an IN lock on the table but no row-level locks.

The maximum requester I/O block size is 64K.

You can configure DB2 to create some agent processes when DB2 is started by setting the NUM_INITAGENTS parameter to a value greater than zero.

To ensure the integrity of your database, DB2 writes the log buffers to disk when:

• One or more transactions commit

• The log buffer is full

• One second has elapsed since the last log buffer flush

Lock escalation will occur when:

• The database lock list becomes full

• Any one application uses more than the MAXLOCKS percent of the lock list

You can capture table and index statistics:

• By running the

  runstats utility

• When loading data into one of your tables

• By running the

  reorgchk utility

The

reorg command not only reclusters the data in the table, but it also removes embedded free space by deleting rows and eliminating overflow records.

The timestamp monitor switch is enabled by default (it is used by the health monitor).

The

reset monitor all command will reset all of the database monitor counters.

You need to create the explain tables to use the Visual Explain tool.

D . The

import command cannot capture statistics.

D . The SOFTMAX configuration parameter controls the percentage of a log file that is filled before the page cleaners are triggered to write dirty pages from the buffer pool(s) to disk.

C . When DB2 performs lock escalation, it converts row-level locks to a table-level lock.

B . The configuration parameter sequential detection (SEQ_DETECT) allows DB2 to detect sequential page reads and trigger prefetching.

B and

D . The page cleaners are triggered when the percentage of dirty pages in any one buffer pool reaches CHNGPGS_THRESH, or when applications write enough information to the logs to reach SOFTMAX percentage of any log file.

A. reorgchk will indicate if a reorg is suggested based on a number of conditions. One of these conditions is the number of overflow records in the table.

B . An overflow record is created when a row in a table is updated, a varchar column is updated, and its length increases so much that it can no longer fit on the same page.

D . DB2 does not support hints, as they are not needed due to the efficiency of the DB2 optimizer.

D . DTSCAN is not an operator used by DB2.

C . The shared sort heap threshold is a hard limit, and an attempt to start the fourth concurrent shared sort would cause that sort to overflow; therefore, the answer is C.