TurboIMAGE/XL Database Management System Reference Manual MPE/iX V6.5 (30391-90011)
412 Chapter8
Using the Database Utilities
DBUNLOAD
Broken Chains
If a chained DBUNLOAD encounters a broken chain, it will unload all entries in the chain
down to, but not including the break. It will then go to the end of the chain and follow the
chain backward to the break, then unload the remaining records of the chain. In some
instances, this will save all entries in the chain. In any case, the order of the entries is
preserved. Information about each broken chain in a data set is printed before the
end-of-the-data-set summary (see statement 4 under "Operation Discussion" in this
section).
Operation Discussion
1 An optional file equation that specifies the device class name for the device
on which the data entries are to be copied. The default is device class
TAPE.
2 Initiates execution of the DBUNLOAD program in the PUB group of the SYS
account.
3 In session mode, DBUNLOAD prompts for the database name and
maintenance word. In job mode, the database name and maintenance
word, if any, must be in the record immediately following the RUN
command.
4 After copying a data set without detecting a broken chain, DBUNLOAD
prints a message that includes the data set number and the number of
entries copied.
If DBUNLOAD detects a broken chain, the following messages are also
returned:
DATA SET
m
: Broken Chain at Entry
#p
[,following Entry
#q
]
Chain Head is Entry
#r
of Data Set
#s
Key =
k
l
entries [expected,
j
entries salvaged]
where:
p
is the entry number where the break was detected.
q
is the number of the entry last unloaded from the front of
the chain, if any.
r
is the entry number of the chain head.
s
is the data set number of the chain head.
k
is the value of the key of the broken chain.
l
is the length of the chain according to the user label.
j
is the number of entries salvaged from the chain.
These four message lines are repeated for every broken chain in the data
set, followed by the end-of-data-set summary that reports the number of
lost entries, if any: