Control Interval is analogous to a physical block for QSAM files. It is the unit of i/o. Must be between 512 bytes to 32 k. Usually either 2K or 4K. A larger control interval increases performance for sequential processing while the reverse is true for random access. Under CICS when a record is locked, the entire CI gets locked.
Control area is a group of control intervals. CA is used during allocation. CA size is calculated based on the
allocation type (cyl, tracks or records) and can be max of 1 cylinder.

it  is used to rename clause only.

its just like dump cmd used in RPGLE. you can able to see variable values used in CL pgm

during the time of compilation of a file , constrains are being removed, from the
file .but at the time of compliation keys are not removed in case from pf. constraints has no affects on members of a pf but keys has affect on members of pf.

copyfile command copies the contents of existing database file into another datbase file .
using cpyf -> we cancopy data from external device to a datbase file and viceversa.
crtdupobj-> create duplicate object, create clone exactly as the source file with structure and content with its link to prgram and logical file and its authority setting as well. no need to recompile pgm that use this file.

Flat file is a physical file which can be created without specifying any DDS levels.
Flat file is a database file with no data defenition specification.we can create a flat file using command CRTPF