An existing data item is one whose name is currently defined to the cache structure. This topic summarizes a way to use the IXLCACHE REQUEST=WRITE_DATA to update an existing data item.

To ensure that you do not overwrite changes that another user might have made to the data item and to ensure that the copy of the data item in your local cache buffer is current, you can code WRITE_DATA with WHENREG=YES without having to use locks to serialize the updates. When coding the WRITE_DATA request for an existing data item, specify the NAME keyword to identify the data item and WHENREG=YES to request that the system perform the update only when you have a registered interest in the data item.

Otherwise, you can use IXLLOCK to serialize your updates and specify WHENREG=NO with the WRITE_DATA request, and the system performs the update regardless of whether you have registered interest in the data item or not.

Your request must indicate whether the data item you are writing is the same as the copy on permanent storage. If it is the same, specify CHANGED=NO or omit the parameter to use the system default. The system does not allow you to overwrite changed data with unchanged data.