Vijay Anandhan
New User
Joined: 25 May 2007
Posts: 1
Location: Chennai
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Hi,
Plan:- A plan is an executable module containing the access path logic produced by the DB2 optimizer. It can be composed of one or more DBRMs and packages. Before a DB2 for z/OS program (with static SQL) can be run, it must have a plan associated with it.
Plans are created by the BIND command. The plan is stored in the DB2 directory and accessed when its program is run. Information about the plan is stored in the DB2 catalog.
Package:- A package is a single, bound DBRM with optimized access paths. By using packages, the table access logic is "packaged" at a lower level of granularity than a plan -- at the package (or program) level.
To execute a package, you first must include it in the package list of a plan. Packages are not directly executed, they are only indirectly executed when the plan in which they are contained executes .
A plan can consist of one or more DBRMs, one or more packages or, a combination of packages and DBRMs.
To help differentiate between plans and packages, consider a grocery store analogy. Before going to the grocery store, you should prepare a shopping list. As you go through the aisles, when you find an item on your list, you place the item in your shopping cart. After your paying for the items at the check-out register, the clerk places your grocery items in a bag. You can think of the purchased items as DBRMs. The bag is the plan. You have multiple DBRMs (grocery items) in your plan (shopping bag).
In a package environment, rather than actually removing the items from the shelf, you would mark on your shopping list the location of each item in the store. Upon checking out, you would give the list to the clerk at the counter. The clerk then would place the list in the bag?not the actual items. The plan (bag) contains a list pointing to the physical location of the packages (grocery items) that are still on the shelf. This approach is a good way to compare and contrast the two different environments. |
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