Read-only protocol

Similar gains in efficiency can be made if the resource manager is in read-only mode throughout the current unit of work (UOW).

Again, a single-phase commit is appropriate. To benefit, the resource manager must return to the TRUE a flag indicating whether the UOW is read-only or not. The flag may show either the “history” of the UOW so far (for example, so far it is read-only), or whether the current request is read-only. In turn, the TRUE must update the UEPREADO flag in the DFHUEPAR parameter list with the history of the UOW so far. That is, it must set UEPREADO initially, but unset it as soon as the UOW contains updates. (Once UEPREADO has been unset, CICS® ignores any subsequent setting of the flag during the current UOW, and treats the UOW as containing updates.)

At the end of the UOW, if the UEPREADO flag is still set, the syncpoint manager invokes the TRUE with instructions to issue a single-phase commit to the resource manager (by setting the UERTELUW bit on).