User Exits in SAP PM

User exits or Customer Exits are the exits made available to program as per user's needs into standard SAP program.  Every transaction is supported by SAP standard ABAP program or it i constituted by sevral standard function module. but if you want to include some enhncements in standard transactions, it is very much helpful.
There are some user exits which are useful and listed below:
- IWMI0001  User exits for SM/PM IDOCs
- IWO10001  Create a PM sub-order
- IWO10002  PM maintenance order: Customer check for order release
- IWO10004  Maintenance order: Customer check for order completion
- IWO10005  Maintenance order: Cust.-specif. determination of profi
- IWO10006  Maint. order: Fcode exclusion through cust. enhancement
- IWO10007  Maint.order: Customer enhancement - permits in the orde
- IWO10008  Cust. enhancement: Determination of tax jurisdiction co
- IWO10009  PM Order: Customer Check for 'Save' Event
- IWO10010  Maint. order: Cust. enhancement for determining WBS ele
- IWO10011  Maint. order: Customer enhancement for component select
- IWO10012  Maintenance order: Priority handling on central header
- IWO10015  Maintenance order: F4 Help for user fields on operation
- IWO10016  PM Order: Cust. enhancement to check operation user fie
- IWO10017  Determine external order number by customer logic
- IWO10018  Maintenance order: User fields on order header
- IWO10020  Maintenance order: Automatically include task list
- IWO10021  Automatic task list transfer when creating order from n
- IWO10022  Determine calendar from user exit
- IWO10023  Service order: Change header data for advance shipment
- IWO10024  Service order: Changes to items for advance shipment
- IWO10025  PM/SM order: Finding responsible cost center
- IWO10026  User check on setting status 'Do not perform'
- IWO10027  User exit: Generate user-defined settlement rule
- IWO10029  Inclusion of bill of material in PM/SM order
- IWO10030  Preset Fields for Event Object