what is isolation level in cognos

[nsaxena]

Hi All ,

I want to understand with simple example what are isolation level in cognos.

Tried referring below link, but if someone can give simple example of its use and purpose...it would be great.
http://www.ibm.com/support/knowledgecenter/SSRL5J_1.0.1/com.ibm.swg.ba.cognos.ug_cra.10.1.1.doc/c_isolationlevels.html%23IsolationLevels

We use db2 database ,and isolation level is set as read uncommitted mostly

Please suggest. Thanks!

[the6campbells]

Ultimately, which isolation levels can be set is determined by the database vendor.
Unless you explicitly direct Cognos BI, the isolation level used for a unit of work is the one which your vendors driver defaults to.
In some cases (i.e. IBM DB2 CLI or JCC) you may have a means to set those values via configuration files/connection options the vendor supports.
The options IBM Cognos BI shows in the UI would be those it would attempt to ask the driver to grant it. Should the one it request fails, it will ask for the next higher level and if that cannot be attained an error should be thrown.

Keep in mind, lowering the isolation level (ie. read uncommitted) may cause your RDBMS to use fewer resources to track locks. This presumes that your system is not trickle loading/changing data, which if it is could result in you reporting data which another application does not commit.

Some vendors offer committed read strategies where the reader does not block a writer. Best to review your vendors architecture documetation re what they offer.

Last, keep in mind that what gets locked (granularity) is driven by the execution plan your RDBMS uses.