a) Immediate Execution

Immediate custom actions, can be sequenced anywhere within any of the sequence tables. It has access to the installation database (read & set installation properties, modify feature & component states, add temporary columns, rows, and tables).

B) Deferred Execution – User Context

Deferred custom actions can only be sequenced between the Install Initialize and Install Finalize actions in execute sequence tables. It doesn’t have access to the installation database. Deferred custom actions are not executed immediately. Instead they are scheduled to run LATER during the execution script. The execution script isn't PROCESSED until the Install Execute, Install Execute Again, or Install Finalize action is run. If the Current User doesn’t have the elevated privileges (Custom actions make changes in the system DIRECTLY), the custom actions should run in Deferred Execution in User Context only.

c) Rollback only

This Action should be executed during the Installation of the Rollback script or if the Installation is Unsuccessful.

d) COMMIT only

This Action should be executed during the Installation of the Commit script.

e) Deferred Execution – System Context

Deferred custom actions can only be sequenced between the Install Initialize and Install Finalize actions in execute sequence tables. It doesn’t have access to the installation database. Deferred custom actions are not executed immediately. Instead they are scheduled to run later during the execution script. The execution script isn't processed until the Install Execute, Install Execute Again, or Install Finalize action is run. If the Current User have the elevated privileges (Custom actions make changes in the system directly), then it should run in Deferred Execution in System Context only.

a) Immediate Execution

Immediate custom actions, can be sequenced anywhere within any of the sequence tables. It has access to the installation database (read & set installation properties, modify feature & component states, add temporary columns, rows, and tables).

b) Deferred Execution – User Context

Deferred custom actions can only be sequenced between the Install Initialize and Install Finalize actions in execute sequence tables. It doesn’t have access to the installation database. Deferred custom actions are not executed immediately. Instead they are scheduled to run later during the execution script. The execution script isn't processed until the Install Execute, Install Execute Again, or Install Finalize action is run. If the Current User doesn’t have the elevated privileges (Custom actions make changes in the system directly), the custom actions should run in Deferred Execution in User Context only.

c) Rollback only

This Action should be executed during the Installation of the Rollback script or if the Installation is Unsuccessful.

d) Commit only

This Action should be executed during the Installation of the Commit script.

e) Deferred Execution – System Context

Deferred custom actions can only be sequenced between the Install Initialize and Install Finalize actions in execute sequence tables. It doesn’t have access to the installation database. Deferred custom actions are not executed immediately. Instead they are scheduled to run later during the execution script. The execution script isn't processed until the Install Execute, Install Execute Again, or Install Finalize action is run. If the Current User have the elevated privileges (Custom actions make changes in the system directly), then it should run in Deferred Execution in System Context only.