gtpd1m2o | Database Reference |
As discussed earlier, an xternalObject is placed in a file record when an
object does not fit in a single control record and has overflowed into one or
more additional records.
- Note:
- In our discussion, we are still referring to the example described in Figure 52.
The following are attributes or fields to look for in a filed
xternalObject:
- XOBJ_OID, which is a field containing the persistent identifier (PID) of
the collection for which TPFCS uses that object. (In our example,
XOBJ_OID would contain the PID of the collection associated with
OBJECTA.)
- XOBJcount, which is the count of overflow records, including the
first. (In our example, XOBJcount would contain three records.)
- One XOBJentry for each primary record. (In our example, there would
be three XOBJentry fields, which include an entry that points to both the
primary and shadow copies of record 1.) Each XOBJentry contains:
- A directory entry containing the file addresses of both the primary as
well as the shadow copy of the record if one exists. The format of
directory entries are also used elsewhere by TPFCS. Unless otherwise
noted, their format corresponds to the first directory entry format discussed
in Record Types.
- The record ID and record code check (RCC) of the record.
You can calculate the exact displacements to these attributes as well as
their lengths by reading the definition of the xternalObject instance in the
TPFCS source code.