There are two parcel header formats:
- Standard Parcel Header (SPH)
- Alternate Parcel Header (APH)
The maximum length of an SPH parcel is 65,535 bytes; the maximum length of an APH parcel is ~1 MB.
A parcel using the APH will be 4-bytes larger than a parcel using the SPH.
The format of the SPH shown in the following figure.
A maximum parcel body size of 65,104 bytes is only approached with the Archive/Recovery utility. The maximum size of a regular SQL parcel body is 64,260 bytes, including overhead such a presence bits and variable length columns.
The format of the APH is shown in the following figure.
The two types of parcel headers may be intermixed in the same request or response. Parcels whose length is less than or equal to 65,535 may use either header format.
- A response only contains a parcel using APH if the APH-response-permitted option was specified and the database supports the alternate header for that parcel.
- dbcarea.consider_APH_resps must be set to ‘Y’ to receive APH responses.