Consider specifying a vector entry that is currently assigned to a data item to another data item if you need to contract the size of your local cache buffer and you want to remap your vector entry indexes to data items so you can keep frequently referenced data items in the contracted local cache buffers.

In the following is a scenario, a protocol maps each vector entry to a named buffer: for example, vector entry 1 maps to BUFONE, vector entry 2 maps to BUFTWO, and so forth. BUFONE contains data item X, BUFTWO contains data item Y, and BUFTHREE contains data item Z. You want to free the space allocated to BUFTHREE and you want to keep data items X and Z in the local cache buffers:

1. Move data item Z from BUFTHREE to BUFTWO.
2. Issue the following request to write data item Z to the cache structure, to assign vector entry 2 to data item Z, and to deregister interest in data item Y:

   IXLCACHE REQUEST=WRITE_DATA,WHENREG=NO,VECTORINDEX=VECTOR2,         X
            NAME=NNAME,OLDNAME=ONAME,…
   ⋮
   VECTOR2  DC  F'2'       VECTOR ENTRY
   NNAME    DC  CL16'Z'    NEW NAME
   ONAME    DC  CL16'Y'    OLD NAME
   ⋮

3. Free the storage allocated to BUFTHREE.
4. Compress the vector, using IXLVECTR MODIFYVECTORSIZE, so that the unneeded entry 3 is released.

For general information on specifying the vector index entry, see Specifying the Vector Entry Index on IXLCACHE Requests.