SAP Developer Keys and Object Keys in ABAP Tables

In SAP systems SAP developer keys are stored in ABAP table DEVACCESS known as "Table for development user" used by DEVELOPER_KEY_CHECK and DEVELOPER_CHECK function modules as reference data. Besides development users and corresponding developer keys ADIRACCESS SAP table stores object keys for TADIR objects in that SAP system.

These ABAP tables can be used to get the list of developer users and SAP objects modified by developers in an SAP system

SAP DEVACCESS Table for Development User

Using SE11 transaction code, ABAP programmers can display the simple structure of DEVACCESS Table for development user

SAP DEVACCESS Table for Development User Keys

As ABAP programmers can easily realize the table is client independent without MANDT field for storing client number in SAP systems

For each user which is being registered as an ABAP developer on that SAP system, the Developer key must be provided specific to that SAP user.
This process is done once for each developer.
SAP CL_WCF_SKEY_API class provides methods for APIs for SKEY functionality like methods:
CHECK_DEVELOPER,
CHECK_TADIR,
GET_INSTALLATION_DATA,
IS_TADIR_CHECK_NEEDED,
REGISTER_DEVELOPER and
REGISTER_TADIR

DEVELOPER_KEY_CHECK and DEVELOPER_CHECK Function Modules

ABAP function modules DEVELOPER_KEY_CHECK and DEVELOPER_CHECK are used for development user check and developer key registration check where DEVACCESS table is queried for the validity status of current user or for the developer key.

SAP System Measurement Statistics for Developer Key Counts

On the other hand, for client based details in an SAP system ABAP programmer can use System Measurement USMM transaction code.
Launch USMM tcode
When System Measurement initial screen is displayed, press Measurement Statistics button.

When the SAP System Measurement Statistics are listed, search for SSCR standing for SAP Software Change Registration, you will see a table with user types per SAP system clients defined as seen in below screenshot.

SAP Software Change Registration SSCR keys by client

ABAP Table ADIRACCESS for TADIR Object Keys

Using SE11 tcode when you query ABAP table ADIRACCESS you can see that the TADIR object keys are stored in that table.

SAP

These objects are probably altered by developers in your SAP system using these keys.
For example if you go to SE38 for an ABAP program listed in table ADIRACCESS, follow menu options:
Utilities > Versions > Version Management
It is possible that ABAP developer changes are displayed in the list.

In order to make changes on SAP sources and SAP dictionary objects Object keys are required.
For each SAP object which is being changed, a new Object key is required.
The Object key is used for the first change registration, for following changes the same key is used and no key is requested by the SAP system.

Please refer to SAP Support Portal for more information on SAP Software Change Registration SSCR keys.