> -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On > Behalf Of (IBM Mainframe Discussion List) > Sent: Tuesday, July 24, 2007 8:07 AM > To: IBM-MAIN@BAMA.UA.EDU > Subject: Re: Is a page protected?--how to determine > > In a message dated 7/24/2007 1:33:11 A.M. Central Daylight Time, > [EMAIL PROTECTED] writes: > >I have a need to determine if an address in storage is page protected > in order to determine if a PGSER UNPROTECT needs to be done. > > One way, not necessarily the most elegant, is to establish an ESTAE or > FRR, > put your program into key 0, and do an OI into any byte in the page with > an > operand of X'00'. This instruction will not change the byte being > accessed, > but if the page is page protected your OI will produce a S0C4 which you > trap > and from which you recover in your recovery routine. If the page is not > page > protected, the next instruction after the OI will execute. > > Bill Fairchild
very bad idea in general. if the page is not protected, then you don't know what other processes are updating that page nor how they serialize their updates. the OI is not an interlocked update and may cause corruption when another CPU is concurrently modifying that byte. Jeffrey D. Smith Principal Product Architect Farsight Systems Corporation 700 KEN PRATT BLVD. #204-159 LONGMONT, CO 80501-6452 303-774-9381 direct 303-484-6170 FAX http://www.farsight-systems.com/ ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
