> -----Original Message----- > From: IBM Mainframe Discussion List > [mailto:[EMAIL PROTECTED] On Behalf Of Lindy Mayfield > Sent: Monday, January 21, 2008 12:34 PM > To: [email protected] > Subject: Re: How does ATTACH pass address of ECB to child?
[snip] > > Lindy > > Things like "atomic" and "compare and swap" are still beyond me right > now. I'll get it sooner or later. "Atomic" is used quite a bit in computer science. Like the original Greek, it means "indivisible". That is, when an atomic operation occurs, any other process will either see the data in the original form, or in the updated form. But it will never seen an intermediate form. It is especially used in relational databases. This is usually done so that, for instance, if you transfer money from checking to savings, you never see the amount in both places. You either see the amount in checking or in savings. This despite the fact that a lot of stuff is going on to do the move. "compare and swap" simply means that. It compares field1 against field2. If field1 equals field2, then the contents of field3 is placed in field2. What is "atomic" is that there is a "lock" that occurs so that at the instant before field1 is compared against field2, no other process is allowed to modify or even look at field2 until after the instruction finishes. This ensures that once the operation starts that no other process can make any updates or decisions based on the contents of field2. -- John McKown Senior Systems Programmer HealthMarkets Keeping the Promise of Affordable Coverage Administrative Services Group Information Technology The information contained in this e-mail message may be privileged and/or confidential. It is for intended addressee(s) only. If you are not the intended recipient, you are hereby notified that any disclosure, reproduction, distribution or other use of this communication is strictly prohibited and could, in certain circumstances, be a criminal offense. If you have received this e-mail in error, please notify the sender by reply and delete this message without copying or disclosing it. ---------------------------------------------------------------------- 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
