The WRITE/NOWRITE usage of a shared table must be consistent on all TBOPEN and TBCREATE requests. That is, all requests for a given shared table that result in concurrent use of that table must specify the same WRITE or NOWRITE attribute.
A successful TBOPEN or TBCREATE request causes the use count in the table to be incremented by one. The use count determines the action taken by subsequent TBEND and TBCLOSE requests.