Tranaction Attributes usage situation

[Koneti Kavi Kumar]

Hi all,   Can any body explain me by giving an example or ref. URL at what situations which attribute is applicable to get better performance of AppServer. Suppose for if it is "select" kind of operation then it would be better to keep "Never" as Tranaction Attribute. In this way can any one explain me abt these attributes usage.     Required RequiresNew NotSupported Supports Mandatory Never     Tanks in advance, Kavi