•
DCOM supports a 512 byte sector disk and a 514 byte internal disk.
•
DCOM does not permit multiple volumes in the command line.
Examples of Compression Output
In its preliminary stage, DCOM produces the same summary report and space-distribution reports
produced by DSAP. For examples of these reports, see
Report Formats (page 101)
.
You can have Enscribe and SQL files on the volume you specify for the DCOM procedures. Space
allocation for SQL file output is not distinguished from space allocation for Enscribe file output in
DCOM. The reports from DCOM are unchanged for SQL file support with one exception: If DCOM
reports a file with double allocated extents, and the message
SQL Shadow
appears after the file
name, the file is an SQL table that was dropped, but the drop is not yet committed. This type of
file is invisible, but its extents are still allocated until the drop is committed.
Before DCOM Moves File Extents
When the compression phase begins (but before DCOM moves any extents), it sends messages
to the event message collector ($0).
Figure 8 Format of DCOM Operator Messages (Before the Move)
While DCOM Moves File Extents
DCOM sends a report to the current output device, denoting each file extent it moves and which
files were directly affected. For example, in "Move Num" 5 displayed in
Figure 9
, DCOM moves
extent #11 of the file XRAYENF.QCACHE from page 52181 on the disk to its new location at
page 5110 on the disk at 12:30 and 22 seconds.
Figure 9 Format of DCOM Report (During the Move)
After DCOM Moves File Extents
When it finishes moving extents, DCOM produces a report.
Figure 10 Format of DCOM Report (After the Move)
•
The first line reports the total number of extents and pages moved.
•
The second line gives the new number of free extents, which are fewer and larger than before
the move, depending on the success of the compression.
•
The third line lists the number of pages in the largest free extent on the disk. To see the
remaining free extents, refer to the space distribution reports that DCOM also produces at this
time.
When compression is complete, DCOM sends operator messages to the event collector.
88
Disk Compression (DCOM)
