How and when to use GU and GHU calls is perfectly needed to write logic in IMS DB programs. Read more.
Useful and most frequently used IMS DB command codes complete list you can read here.
Many programmers not aware how to handle U0777 error that occurred for dead lock scenario in IMS DB database. There is a simple solution available for this. While writing your program just follow these steps, so that you will not be received an error U0777
IMS DB Mandatory statement is DLITCBL for all COBOL and IMSDB programs. Read for full details