v$type_size

v$type_size該檢視列出各種資料庫元件的尺寸以估計資料塊的容量。使用這個檢視可以很方便的知道各個元件的大小。以前不知道這個檢視，為了得到TRANSACTION VARIABLE HEADER和DATA HEADER進行了大量的實驗，呵呵。

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SQL> select * from v$type_size;

COMPONEN TYPE DESCRIPTION TYPE_SIZE
-------- -------- -------------------------------- ----------
S EWORD EITHER WORD 4
S EB1 EITHER BYTE 1 1
S EB2 EITHER BYTE 2 2
S EB4 EITHER BYTE 4 4
S UWORD UNSIGNED WORD 4
S UB1 UNSIGNED BYTE 1 1
S UB2 UNSIGNED BYTE 2 2
S UB4 UNSIGNED BYTE 4 4
S SWORD SIGNED WORD 4
S SB1 SIGNED BYTE 1 1
S SB2 SIGNED BYTE 2 2
S SB4 SIGNED BYTE 4 4
S BOOLEAN BOOLEAN 4
S FLOAT FLOAT 4
S DOUBLE DOUBLE 8
S SIZE_T SIZE_T 8
S DSIZE_T DSIZE_T 4
S PTR_T PTR_T 8
K KDBA DATABASE BLOCK ADDRESS 4
K KTNO TABLE NUMBER IN CLUSTER 1
K KSCN SYSTEM COMMIT NUMBER 8
K KXID TRANSACTION ID 8
K KUBA UNDO ADDRESS 8
KCB KCBH BLOCK COMMON HEADER 20
KTB KTBIT TRANSACTION VARIABLE HEADER 24
KTB KTBBH TRANSACTION FIXED HEADER 48
KTB KTBBH_BS TRANSACTION BLOCK BITMAP SEGMENT 8
KDB KDBH DATA HEADER 14
KDB KDBT TABLE DIRECTORY ENTRY 4
KTE KTECT EXTENT CONTROL 44
KTE KTECH EXTENT CONTROL 72
KTE KTETB EXTENT TABLE 8
KTS KTSHC SEGMENT HEADER 8
KTS KTSFS SEGMENT FREE SPACE LIST 20
KTS KTSPHW PAGE TABLE SEGMENT HWM 60
KTS KTSPHC PAGE TABLE SEGMENT HEADER 112
KTS KTSPFHC LEVEL 1 BITMAP BLOCK HEADER 184
KTS KTSPSHC LEVEL 2 BITMAP BLOCK HEADER 96
KTS KTSPTHC LEVEL 3 BITMAP BLOCK HEADER 88
KTU KTUBH UNDO HEADER 16
KTU KTUXE UNDO TRANSACTION ENTRY 40
KTU KTUXC UNDO TRANSACTION CONTROL 104
KDX KDXCO INDEX HEADER 16
KDX KDXLE INDEX LEAF HEADER 32
KDX KDXBR INDEX BRANCH HEADER 24