> I've studied the manuals but before I start coding to use a Common > Data Space I want to confirm that for a common data space access is > by the PASN-AL and the ALESERV creates a PASN-AL for all the addressspaces.
All of the PASN-AL entries for SCOPE=COMMON data spaces are built when a PASN-AL is built during address space creation (to avoid the need for ALESERV ADD,AL=PASN to update the PASN-AL of every address space when a SCOPE=COMMON data space is being added. The ALESERV ADD in this case simply determines what the ALET should be and returns that to the caller. > So all I have to do is issue the DSPSERV > CREATE,TYPE=BASIC,SCOPE=COMMON and ALESERV ADD,AL=PASN once and pass > the ALET to all address spaces that access this dataspace. Correct? Correct. > Is there additional overhead accessing data spaces as opposed to > accessing primary storage? (I expect not) When an access register reference misses in the ALB, the processor must perform Access Register Translation before performing Dynamic Address Translation. So there is additional overhead for ALB misses. Also, there is the overhead in your program for the management of the access registers. Also, the systems programmer needs to plan for the number of SCOPE=COMMON data spaces via the MAXCAD parameter in IEASYSxx. z/OS 1.10 introduced the support for 64-bit common storage, so unless you need run on an older release, 64-bit common may be a better choice than a SCOPE=COMMON data space. > If an address space is created after the ALESERV macro is executed, > can the new address space access the data space? Yes. Jim Mulder z/OS System Test IBM Corp. Poughkeepsie, NY ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
