CREATE TABLE CALC$DETAIL (
    DET_ID           INTEGER NOT NULL,
    ....
    DET_SRC          INTEGER,
    ....
);


ALTER TABLE CALC$DETAIL ADD CONSTRAINT FK_DET_SRC FOREIGN KEY (DET_SRC) REFERENCES CALC$SOURCE (SRC_ID) ON DELETE CASCADE;

CREATE TABLE CALC$SOURCE (
    SRC_ID         INTEGER NOT NULL,
    ....
);

ALTER TABLE CALC$SOURCE ADD CONSTRAINT PK_CALC$SOURCE PRIMARY KEY (SRC_ID);

c:\Program Files\Firebird\Firebird_3_0>gstat -h c:\Temp\BK_REST\FIN.GDB

Database "C:\TEMP\BK_REST\FIN.GDB"
Gstat execution time Wed Nov 11 10:59:12 2020

Database header page information:
        Flags                   0
        Generation              1416630
        System Change Number    0
        Page size               8192
        ODS version             12.0
        Oldest transaction      1793522
        Oldest active           1793523
        Oldest snapshot         1793523
        Next transaction        1793532
        Sequence number         0
        Next attachment ID      5591
        Implementation          HW=AMD/Intel/x64 little-endian OS=Windows CC=MSV
C
        Shadow count            0
        Page buffers            0
        Next header page        0
        Database dialect        3
        Creation date           Oct 25, 2020 21:08:02
        Attributes              force write, no reserve, multi-user maintenance

    Variable header data:
        Sweep interval:         20000
        *END*
Gstat completion time Wed Nov 11 10:59:12 2020

MAXIMUM2	Tue Nov 10 15:38:13 2020
	Database: C:\TEMP\BK_REST\FIN.GDB
	Error: Data page 1680194 {sequence 5106} marked as secondary but contains primary record versions in table CALC$SOURCE (243)


MAXIMUM2	Tue Nov 10 15:38:13 2020
	Database: C:\TEMP\BK_REST\FIN.GDB
	Warning: Pointer page 426570 {sequence 3} bits {0x08 secondary} are not consistent with data page 1680194 {sequence 5106} state {0x00 } in table CALC$SOURCE (243)

MAXIMUM2	Tue Nov 10 15:38:50 2020
	Database: C:\TEMP\BK_REST\FIN.GDB
	Warning: Page 1677296 is an orphan