Format for data element header

The data element header contains fields that describe the type and length of data being logged as well as options for z/OS® compression services.

The following table lists the format for data element headers.

Table 1. Format for log record header
Field name Data type Field description
LOGID XL1 The type of data being logged.
  • X'00'- CAPD block
  • X'04'- DBD Version ID
  • X'08'- Physical concatenated key
  • X'0C'- CAPD_DATA
  • X'10'- Segment data
  • X'14'- Before-image data
LOG_FLAGS XL1 Flags. Bit definitions follow:
COMPR_DATA X'20' The data is compressed using z/OS compression services.
  X'10' Reserved for future use.
  X'08' Reserved for future use.
  X'04' Reserved for future use.
  X'02' Reserved for future use.
  X'01' Reserved for future use.
LOG_LL H Length of LOG_DATA.
LOG_DATA CL0 Log data that is compressed if the z/OS services are available. The 4-byte data element header is followed by the type of data that is being logged:
X'00'
CAPD block
X'04'
The log data is the DBD Version ID.
X'08'
The log data is the physical concatenated key.
X'0C'
CAPD_DATA
X'10'
The log data is the Segment data.
X'14'
The log data is the Before-image data.

Before-image data is preceded by a halfword offset of the changed data within the segment. The halfword offset is not compressed.