Important SAP Tcodes

ABAP & Tables Related Transactions
SA38 To execute a Abap program
SE38 ABAP Editor
SE11 ABAP/4 Dictionary Maintenance
SE80 ABAP Development Work Bench
SE16N General Table view ( very Useful)
SE16 Data Browser or table viewer

Administration
AL11 Display SAP Directories
BD54 Maintain Logical System
OSS1 Logon to Online Service System
SALE IMG Application Link Enabling(ALE)
SARA System Archive Administration
SCU0 Customizing Cross-System Viewer
SICK Installation Check (System Initial Consistency Check)
SM01 Lock/unlock Transactions
SM02 Send System Messages to all users
SM04 List of Users logged into the Client
SM12 Display and Delete Locks
SM13 Display Update Request Records
SM14 Update Program Administration
SM21 System Log
SM35 Batch Input Overview
SM50 Work Process Overview
SM51 SAP Servers list
SM56 Number Range Buffer
SM58 Transactional RFC overview
SM59 Display and Maintain RFC Destinations
SM66 Global Work Process Overview
SAINT SAP Add-on Installation Tool
SPAM SAP Support Package Manager (SPAM)
SPAU Display modified DE objects
SPDD Display modified DDIC objects
ST11 Display Developer Traces
ST22 ABAP/4 Runtime Errors
SU56 User Buffers
SMT1 Maintain or display Trusted systems



Client Administration commands
SCC3 Client Copy Analysis Log
SCC4 Client Administration
SCC5 Client Delete
SCC7 Client Import Post-Processing
SCC8 Client Export
SCC9 Remote client copy
SCCL Local Client Copy
SCC1 Client Copy by transport request


Configuration
FILE Cross-Client File Names/Paths
RZ04 Maintain Operation Modes and Instances
RZ10 Maintenance of Profile Parameters
RZ11 Profile parameter maintenance
SE93 Maintain Transaction Codes
SWU3 Automatic Workflow Customizing
SPRO Customizing: Execute project
SM63 Display/Maintain Operating Mode Set


Database Administration
DB01 Analyze exclusive lockwaits (database snapshot)
DB02 Analyze tables and indexes (Space History overview)
DB03 Configuration Parameter Changes
DB12 DB Backup and Recovery Monitor
DB13 DBA Planning Calendar
DB15 Tables and archiving objects


Background Jobs
SM36 Define or schedule a Background Job
SM37 Background Job Overview & Maintenance
SM49 Execute External Operating System commands
SM62 Display or maintain Events
SM64 Trigger Event in backgroung processing
SM65 Background Processing Analysis Tool (testing)
SM69 Display or Maintain External OS Commands


Monitoring
AL04 Sap Performance Monitor
AL16 Operating System Monitor
RZ20 CCMS Monitoring
AL08 Current Active Users
OS01 LAN check by ping
RZ01 Job Scheduling Monitor (external program)
RZ03 Presentation, Control SAP Instances
ST01 System Trace
ST02 Setups/Tune Buffers
ST03 Performance, SAP Statistics and Workload analysis
ST03n Work load Analysis
ST04 Performance: Database snapshot
ST05 Performance Analysis
ST06 Operating System Monitor
ST07 Application monitor : User distribution
ST10 Table call statistics
STAT Local transaction statistics

Spool
SP01 Output Controller
SP02 List of the users spool requests
SP11 TemSe directory
SP12 TemSe Administration
SPAD Spool Administration (defining printers etc…)

Transports
SE01 Transport Organizer
SE06 Set Up Workbench Organizer (Post-installation actions for transport organizer)
SE07 CTS Status Display (import monitor)
SE09 Workbench request Organizer
SE10 Customizing request Organizer
STMS Transport Management System
SM30 Table View Maintenance
SM31 Table Maintenance

User Administration
PFCG Profile Generator (Activity Group Maintenance)
SU01 User Maintenance (single user maintenance)
SU01D User Display (safe)
SU02 Maintain Authorization Profiles (depreciated)
SU03 Maintain Authorizations
SU05 Maintain Internet users
SU10 User Mass Maintenance (You cannot change user master data using this)
PFUD User Master Data Reconciliation
SMLG Maintain Logon Group
SUPC Mass generation of Profiles for activity groups
SUIM User Information system (very good transaction code)
One can find any information about a user using this t-code


Central User Administration
SCUA Activate/maintain CUA
SCUG Transfer user
SCUL Central User Management Log Transaction used to view CUA audit and error logs.

Related to Idocs
WEDI IDoc and EDI Basis
WE02 IDoc list display
WE07 IDoc statistics
WE46 IDoc administration

Other Transactions
HIER Internal Application Component Hierarchy Maintenance
WE20 Maintain Partner profiles
WE21 Port definition
WE47 Status Maintenance