"Menon" <rm*******@gmail.com> wrote in message
news:11*********************@c13g2000cwb.googlegro ups.com...
Thanx.
So this is because db2 does not support "read consistency" as supported
by Oracle, correct?
Thus in the case of db2, if you do a select on a lob and you start
updating
I guess at that point db2 would lock the row so that others can not
update it?
Sorry if the questions are basic - am not familiar with the db2 ...
The isolation level determines how long read locks are held. DB2 has the
following Isolation levels:
RR - Repeatable Read - Holds the share lock on all rows accessed. Releases
locks at next SQL commit.
RS- Read Stability - Hold share lock on all rows accessed. Releases locks
when SQL select statement finishes.
CS - Cursor Stability - Holds share lock on all rows accessed. Releases
locks when finished accessing a particular row (when DB2 read the next
row)..
UR - Uncommitted Read - No locks held (dirty read).
No other SQL statement can update a row while a share lock is being held,
but other share locks can coexist.
There is no lock contention for SQL statements in the same unit of work
(same application program). A share lock does not block an update by the
same program (only blocks others).
Isolation levels can be specified in numerous different ways, including in
each individual SQL statement. The default is CS.