The PROTECT option of PGSER makes a range of virtual storage pages read-only and helps to improve data integrity. The UNPROTECT option of PGSER makes a range of virtual storage pages modifiable. You can protect private storage both above and below 16 megabytes.
IBM® recommends that you use PGSER PROTECT only for full pages of storage on page boundaries. This usage avoids making other areas of storage read-only unintentionally. For instance, if you obtain a virtual storage area smaller than a page and then issue PGSER PROTECT, the entire page is made read-only, including the portion of the page that is not part of your storage area.
The system does not keep track of how many times a page has been protected or unprotected. One UNPROTECT cancels all PROTECTs for a given page.