FYI
What is the RM Chain?
The Progress Database manager maintains a list of blocks in the
database which have free space in them, and are therefore eligible for
record additions. This list is called the RM Chain. It is important
to note that this list does not contain ALL blocks in the database;
only those with space available for additions or updates.
How space is allocated for records?
To find space to store a record, or a record fragment, the database
manager first looks at the RM chain to see if an existing record block
with unused space is available. If the block at the head of the RM
chain contains enough space to store the fragment while still leaving
expansion space, and the block has unused record slots, then that
block is used. The record is copied to the block and the amountof
unused space in the block is updated.
If the block at the head of the RM chain cannot be used to store the
record, and it has less unused space than the free space constant, or
if all 32 record slots have been used, it is removed from the RM
Chain. Otherwise, it is moved to the tail end of the chain. In either
case, the next block on the front of the RM Chain is considered and
the process is repeated until sufficient space has
been found or the search limits have been reached.
To limit the search time, no more than 100 blocks on the RM Chain will
be examined and removed from the chain at a time. No more than three
blocks at a time will be examined and moved to the tail end. If either
of these limits is exceeded during a search for space, the search for
reusable space is abandoned and a free block is used.
If no existing record block can be used, an unused block is allocated.
The block is formatted as an RM block, and the record is stored in it.
If the block is already on the RM chain, but now has less free space
than the free space constant, or all the record slots are filled, then
the block should be removed from the RM Chain. But, since the RM
Chain is linked only in for forward direction, it can only be removed
if it is the first block on th echain. If it is not the first block,
it will be left in the chain. It will be removed later
while searching for record space, if it should become the first block
on the chain during the search.
FIX:
This message represents no harm to the database, no measures need to
be adopted.
The determination that the block does not have enough space or record
slots to be on the RM Chain is what produces the (3896) message. Since
the RM Chain is a singly-linked list, removing the block would require
unnecessary effort. During normal operations, when the block gets to
the head of the RM Chain, it will be removed from the list.
