following 3 i frequently use hence sharing with you
a. Comand to know schema of ABAP Stack
db2 " select tabschema from syscat.tables where tabname = 'SVERS' "
b. select and delete sap*
db2 "select bname ,mandt from sap<sid>.usr02 where bname='SAP*'"
db2 "delete from sapsol.usr02 where bname='SAP*'
c. know the concept of DB manager or DBM and its difference with an DB instance. rest all is just like oracle. 
d. reference