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Note: This e-mail is subject to the disclaimer contained at the bottom of this message. _______________________________________________________________________________________ >Date: Mon, 7 Sep 2009 17:54:13 -0400 >From: Pinnacle <pinnc...@rochester.rr.com> >Subject: Re: LLA update > >---- Original Message ----- >From: "Peter Relson" <rel...@us.ibm.com> >Newsgroups: bit.listserv.ibm-main >Sent: Friday, September 04, 2009 7:43 AM >Subject: Re: LLA update > >Peter, > >Can you point us to a statement in IBM documentation that clearly says that >LLA is only designed for use with load modules? My understanding is the >same as many others on this list, that the first "L" in LLA was changed from >LINKLIST to LIBRARY many moons ago. > >Regards, >Tom Conley [Stephen Hall] Tom, >From the ABC's of System Programming Vol 1 (with Snippage): Library Lookaside (LLA) LLA is a z/OS function that improves system performance by reducing the amount of I/O needed to locate and fetch load modules from DASD storage (PDS data sets). The main advantage of using a PDS is that, without searching the entire data set, you can retrieve any individual member after the data set is opened. - LLA maintains, in an LLA address space, copies of the PDS directories. To fetch a module, the system first searches the directory for the load module location in the PDS data set. The system can quickly search the LLA copy of a directory in virtual storage instead of using costly I/O to search the directories on DASD. - LLA places copies (staging) of selected load modules in a Virtual Lookaside Facility (VLF) data space (when the LLA class is defined to VLF). VLF is another z/OS component in charge of keeping load modules and specific data in virtual storage, to avoid I/O operations; refer to "Virtual Lookaside Facility (VLF)" on page 103. for more information about this topic. - LLA determines which modules, if staged, would provide the most benefit to module fetch performance. LLA evaluates modules as candidates for staging based on statistics LLA collects about the members of the PDS data sets it manages, such as module size, fetch count, and the time required to fetch a particular module. The benefits of LLA apply only to load modules that are retrieved through the system functions LINK, LOAD, ATTACH, XCTL, and XCTL. Directory entries for the primary system library (SYS1.LINKLIB), load modules libraries concatenated to it as declared in LNKLSTxx member of SYS1.PARMLIB, and additional production libraries named in SYS1.PARMLIB(CSVLLAxx) are read into the private area of the LLA AS during its initialization. Subsequent searches for programs in these libraries begin with the directories in LLA, and not in the directories on DASD. You obtain the most benefit from LLA when you have both LLA and VLF functioning together. This can be achieved by defining the LLA class to VLF and starting VLF, so the most active modules from LLA-managed libraries are staged into the DCSVLLA VLF data space. Regards, Stephen Hall _______________________________________________________________________________________ The information transmitted in this message and its attachments (if any) is intended only for the person or entity to which it is addressed. The message may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon this information, by persons or entities other than the intended recipient is prohibited. If you have received this in error, please contact the sender and delete this e-mail and associated material from any computer. The intended recipient of this e-mail may only use, reproduce, disclose or distribute the information contained in this e-mail and any attached files, with the permission of the sender. This message has been scanned for viruses with Symantec Scan Engine and cleared by MailMarshal. _______________________________________________________________________________________ ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
