There are two formats of parcel headers. The parcel headers are symbolically defined in the TC2XPH file. The format of the first is:
| Field Name | Offset | Length | Description |
|---|---|---|---|
| PH0FLAVR (FLAVOR-FLAG for COBOL 'flavor' for C, and PL/I) | 00 | 1 bit | A binary zero, indicating this header format. The mnemonic for the bit is PH0FALT ('Tc2ph_Alternate' for C, TPH0_ALTERNATE for PL/I). |
| PH0FLAVR ('flavor' for COBOL, C, and PL/I) | 0.1 | 15 bits | An unsigned integer identifying the type of parcel body. |
| PH0LEN ('length' for C and PL/I) | 02 | 2 bytes | An unsigned integer specifying the length of the parcel, in bytes, including the parcel header and any body. |
The format of the second is:
| Field Name | Offset | Length | Description |
|---|---|---|---|
| PH1FLAVR (FLAVOR-FLAG for COBOL 'flavor' for C and PL/I) | 00 | 1 bit | A binary zero, indicating this header format. The mnemonic for the bit is PH1FALT ('Tc2ph_Alternate' for C, TPH1_ALTERNATE for PL/I) |
| PH1FLAVR ('flavor' for COBOL, C, and PL/I) | 0.1 | 15 bits | An unsigned integer identifying the type of parcel body. |
| PH1FILL1 ('fill1' for COBOL, C, and PL/I) | 02 | 2 bytes | Not used: Set to binary zeroes. |
| PH1LEN ('length' for C and PL/I) | 04 | 4 bytes | An unsigned integer specifying the length of the parcel, in bytes, including the parcel header and any body. |
A response will only contain a parcel with the enlarged header if the APH-response-permitted option was specified and the database supports the alternate header for that parcel. Furthermore, parcels whose length is less than or equal to 65535 may use either header format.