What are different isolation levels in Db2?
Table of Contents
What are different isolation levels in Db2?
Summary of isolation levels
| Isolation level | Access to uncommitted data | Nonrepeatable reads |
|---|---|---|
| Repeatable read (RR) | Not possible | Not possible |
| Read stability (RS) | Not possible | Not possible |
| Cursor stability (CS) | Not possible | Possible |
| Uncommitted read (UR) | Possible | Possible |
What is the default isolation level in Db2?
The cursor stability fetches only committed rows for the program to access. This is a default isolation level. Read stability (RS) – This isolation level places a lock on all the rows which qualifies the SQL statement’s predicate (eg: WHERE clause). The lock is retained until the entire processing is completed.
What are different isolation levels in SQL?
Remarks
| Isolation Level | Dirty Read | Non-Repeatable Read |
|---|---|---|
| Read committed | No | Yes |
| Repeatable read | No | No |
| Snapshot | No | No |
| Serializable | No | No |
What are isolation levels in mainframe?
Summary of isolation levels
| Isolation level | Access to uncommitted data | Phantom reads |
|---|---|---|
| Repeatable read (RR) | Not possible | Not possible |
| Read stability (RS) | Not possible | Possible |
| Cursor stability (CS) | Not possible | Possible |
| Uncommitted read (UR) | Possible | Possible |
Where do we specify isolation level in DB2?
The isolation level is specified during the program preparation process by setting the ISOLATION bind or precompile option. For dynamic SQL statements, the default isolation level is the isolation level that was specified for the package while the statement was prepared.
What is lock in DB2?
The mode of a lock tells what access to the locked object is permitted to the lock owner and to any concurrent processes. Db2 uses of the lock modes to determine whether one lock is compatible with another. Some lock modes do not exclude all other users.
In which isolation level phantom rows can occur in db2?
In Repeatable Read (RR) isolation mode, locks are automatically released from data opened for reading but never read. With RR, if the application returns to the same page and re-reads the row, the data cannot have changed. If a SELECT statement is issued twice in the same transaction, “phantom rows” can occur.
Which isolation level prevents phantom read?
PHANTOM reads can be prevented by using SERIALIZABLE isolation level, the highest level. This level acquires RANGE locks thus preventing READ, Modification and INSERT operation on other transaction until the first transaction gets completed.
