below is from above link
Uncommitted Read (UR)
UR means that a program can read data that has not yet been committed by another program. No locks are taken except for the special S mass delete lock used to serialize UR readers and mass deleters, which requires an X mass delete lock. In addition, an IX lock on any tablespace in the work file database (DSNDB07, usually) is taken to avoid a drop of the tablespace that is being processed. UR, like all of the isolation levels, causes SQL to be serialized with most utilities, depending on the phase of processing, by using claim and drain processing.
If using UR, your program can be reading data that is in the process of being changed. It provides a high level of concurrency. However, do not use UR if seeing uncommited data could affect a business decision.
No comments:
Post a Comment