Free space element anchor point (FSEAP)

Free space element anchor points (FSEAP) are made up of two 2-byte fields.

The first field contains the offset, in bytes, to the first free space element (FSE) in the CI or block. FSEs describe areas of free space in a block or CI. The second field identifies whether this block or CI contains a bitmap. If the block or CI does not contain a bitmap, the field is zeros. One FSEAP exists at the beginning of every CI or block in the data set. IMS automatically generates and maintains FSEAPs.

An FSEAP is shown in the following figure.

Figure 1. An FSEAP
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The FSEAP in the first bitmap block in an OSAM data set has a special use. It is used to contain the DBRC usage indicator for the database. The DBRC usage indicator is used at database open time for update processing to verify usage of the correct DBRC RECON data set.