On 29-Mar-2012 07:07 , Paul Therrien wrote:
INZPFM is an interesting command. I didn't know it existed. And the
idea that one could initialize with deleted records seems odd. It
almost seems to be too specialized of a command to be part of the
operating system. (This is just me musing.)
A side effect of having an "Integrated Database" I suppose; i.e. the
database is an integral part of the OS, so consequentially a number of
OS commands will provide an [possibly very direct] interface to the
database activity. Other databases might be an add-on to the OS and
consequentially the capability for OS commands to impact the non-OS
database files could be generally undesirable.
Ignoring the origins for the capability, consider that a database
file with the attribute of RUSEDLT(*YES) to enable reuse of deleted
records can take advantage of a feature to improve insert performance;
i.e. concurrent insert, which I believe was even noted in a recent
thread about extents which also is relevant to insert performance.
As for being able to add deleted records, because an inserted deleted
rows does not populate the file as\with an "active record", they are
generally innocuous with regard to impact on business rules; i.e. as
alluded, no impact on triggers, constraints, applications waiting-on new
rows or reading either by key or sequentially, etc. Then because a
deleted row can be positioned-to like any other record when employing
"direct" positioning requests, as with OVRDBF POSITION(*RRN &rrn), an
update to that record makes that row\RRN become an active\undeleted
record. That capability allows data copy from an active row to a
previously deleted row, as implementation for reorganizing to compress
deleted rows [from the lower RRN of the dataspace to the end, such that
the database can eventually be truncated of only since-deleted RRNs].
A very important aspect for the capability is the value for a deleted
row to mimic effects of journaled operations which might need to insert
a row RRN-78 but for which presently, the last RRN=70. Understanding
that concurrent activity with isolation can give rise to and thus make
sense of that seemingly illogical scenario.
The I\O feature for adding deleted records is the program QDBPUTD. A
search of the web for that program name will reveal HA references; i.e.
mimic journal apply activity to synchronize data.
Regards, Chuck
midrange.com
