What is th difference between Sap lock and database lock?

A "SAP lock" is named "enqueue lock", the enqueue is on a much higher level, e. g. a complete sales document is locked there whereas in the datbase usually only row locks exist. Since SAP runs on more database than Oracle (thanx god) one needed to have a mechanism, that is database independent and on a higher level.

What is the diff between clients  000 and 001?

Client 000 is the SAP source client, client 001 exists only on certain installations (e. g. solution Manager).  *-- Markus

I would like to know is there anyway to transport roles from Production to Development or Sandbox.

Goto PFCG and enter the role which you want to transfer to other system. goto utilities->Mass download it will ask the path where to download/save that role on local desktop give the location and save it. Next logon to the system where you want that particular role. 
PFCG-> Role -> upload.
Give the path where the role is saved. it accepts and generates successfully.  *-- Mahesh 

What is the need of having Development system?

To develop and custamize SAP to companies requirement. say if you dont have DEV, after go-live(started using SAP (PRD}) if you want to do some changes to application, you cannot do changes directly to PRD server, which may cause problem the PRD server live data. so you do the required changes on DEV first and test them on QAS, if it works fine 
them transport the same to PRD. 

Difference between Application server and Central Instance?

AS: Is just a dialog instance.
CI: Is Dialog instance + Database Instance.

What is Transport domain and Domain controller?

TD: is the collection of transport controller, trans directory and all other systems in the group. 

TC: A system which will have trans directory, and in which the total landscape is designed and maintained. in stms you can see all these.  *-- Suneel

What are SNOTES ? How to apply them in SAP ?

The name of the transaction is SNOTE. A "note" in general is a hint, documentation, error/bug description and may contain code corrections, that are applied with the transaction SNOTE.

What is OSS ?

OSS is the old name of the nowadays "sapnet" which contains everything you need to run SAP a program, patches, installation/upgrade documentation etc.

What are different modules used like EP, XI, CRM ,BW, etc?

Those are not different modules but different products.

EP = Enterprise Portal
XI = Exchange Infrastructure
CRM = Customer Relationship Management
BW = Business Warehouse (that is the old term), it's now call BI (Business Intelligence)

What is the correct use of SPAM, SAINT, SPAD and SPDD transactions. When should we use each?

SPAM is for installing support packages, SAINT is used to install new addons. SPAD is for creating printers (I assume you meant SPAU) and SPDD is for adjusting modification to dictionary objects.

Is it possible to update Support Release packages from OS level?

No - you can import them but the full process will require additional steps the tools "tp" and "R3trans" are not aware of. The way is to use SPAM - but SPAM has the possibility to schedule those imports in the background.

After doing any Support Package update in SPAM, are there any further steps to carry out for this update to take effect?

No, they are active immediately.  *-- Markus

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