Changing the Number of Entries in a Local Cache Vector

The MODIFYVECTORSIZE request allows you to change the number of entries in your local cache vector so you can maintain concurrent registered interest in a different number of data items.

Reducing the size of your local cache vector when it is larger than necessary frees storage for the local cache vectors of other users on your system.

The number of vector entries must be a multiple of 32. If the value you specify is not a multiple of 32, the system rounds the value up to a multiple of 32.

Use the VECTORLEN parameter to indicate the new number of entries you would like your local cache vector to contain. The number of entries the system actually assigns to your local cache vector is returned to you as output through the ACTUALVECLEN parameter.

Decreasing the Number of Entries: If you request a decrease in the number of entries in your local cache vector, your request will always be satisfied.
When a local cache vector's size is decreased, the number of entries is reduced by removing entries starting with the highest number. The remaining entries are unchanged and retain their original values (valid or not valid).

Before eliminating any entries, you must ensure that the entries that will be deleted are not associated with any data items.

If multiple users could be accessing vector entries concurrently, you should obtain exclusive serialized access to the vector before decreasing its size. Otherwise, users that issue the TESTLOCALCACHE or LTVECENTRIES request must be prepared to handle a return code of IXLRETCODEINDXINVALID, indicating that the specified vector index is no longer valid.
Increasing the Number of Entries: If you request an increase in the number of entries in your local cache vector and the system is unable to obtain sufficient storage to satisfy your request, the new number of entries could be unchanged or smaller than what you requested. In this case, the value returned in ACTUALVECLEN will be smaller than the requested number of entries and you will receive return code IXLRETCODELESSTHAN to inform you of the result.
When a local cache vector's size is increased, the number of entries is increased by adding additional entries after the current highest-numbered entry. Existing entries are unchanged and retain their original values (valid or invalid). New entries are initialized to the invalid state.