- User Quotes
The EMC Disk Library for mainframe (DLm) is a Virtual Tape Library for IBM compatible mainframes. All the "tape drives" in an DLm are emulated devices where tapes are actually disk files located on backend storage. Each DLm VTE (node) is attached to an IBM compatible mainframe using FICON or ESCON channels, and typically connects to backend NAS storage using dual-channel gigabit network connections.
DTS Software leveraged existing DTS technology to create the DLm Control Center (DCC). The new product borrows components from SCC Monitor, the Allocation Control Center (ACC), and Easy/Exit.
Note: DCC was originally developed for the Bus-Tech Mainframe Data Library (MDL), and was originally called the "MDL Control Center (MCC)". After EMC purchased Bus-Tech, MCC was renamed to "DLm Control Center (DCC)".
DCC is designed to:
ease a DLm installation
manage the devices through the channel interface using a system console, TSO/ISPF, a PC GUI application, and/or an Apple iPhone/iPad.
monitor DLms using the channel or SNMP TCP/IP interface to trap important DLm events, and then notify support personnel via logs, console or TSO messages, email, and/or text messages. Note: Virtuent 7 firmware is currently required for monitoring through the channel interface.
control OS device allocation without using an SMS Manual Tape Library (MTL) - JES2 and JES3 supported
JCL keyword extensions for DLm Allocation (IBM z/OS only)
perform load balancing for multi-VTE DLm configurations - JES2 and JES3 supported
provide a tape migration tool specifically designed for the DLm
provide scratch exits to keep Tape Management and DLm scratch pools synchronized
designed for IBM z/OS, Hitachi VOS3 and Fujitsu MSP
designed for the EMC Virtuent 6 (DLm 2.x) and Virtuent 7 software releases
When a EMC DLm configuration is installed at a customer site, from an operating system point of view, the DLm VTEs are simply groups of tape drives. From an operations standpoint, the DLm presents several challenges which DLm Control Center (DCC) has been designed to address:
DCC can interface to DLms through the channel interface. For command processing, the product temporarily reserves a device in a DLm VTE for command execution. As soon as the command completes, the device is released. DCC can issue commands from:
- operator consoles
- batch jobs
- the SCC Explorer PC GUI application from DTS Software
- an Apple iPhone or iPad
The new product also has the ability to monitor the DLm event log using either the Channel Interface or SNMP. Event triggers can be used to log messages to a data set, SMF records, and/or send messages to operations staff via the operator console, email or text messages. Note: Monitoring a DLm through the channel interface requires Virtuent 7 firmware.
To streamline the migration process, DTS Software provides the DLMCLONE migration utility. Exact copies of tapes are created in a EMC DLm library using the same volume name and device type. The system catalogs and tape management systems are not affected - only the "location" of the tape is changed. The application also corrects records in the Tape Configuration Database (TCDB). To aid migration throughput, the DLMCLONE utility can perform up to 99 concurrent tape copies to migrate tapes to a DLm.
The DCC DLm Allocation interface can be used to control device allocation. If a requested tape resides in a DLm library, only the library devices are eligible for the allocation request. When non-library tapes are requested, DLMALLOC removes the DLm tape devices from the eligible device list. The interface can also perform unit affinity splits if DD statements try to share the same device, but volumes between the DDs are inside/outside the DLm. Lastly, DCC identifies the condition where a multi-volume tape dataset uses volumes inside/outside the DLm. In this case, the product uses installation defined rules to handle the conditions. By default, the rules issue a warning message, and then terminates the job.
In JES2 environments, DLMALLOC works with MVS Allocation to direct tape requests. In JES3 environments were JES3 SETUP processing is used to select devices before job initiation, DLMALLOC uses two JES3 user exits to direct tape requests to the appropriate devices.
Mainframes have historically been very good at optimizing I/O performance on channels connections. However, installations that have multi-VTE DLm configurations present serious optimization challenges. Due to the number of emulated devices on each VTE, and the inability to access the I/O load on the network connections to the backend storage, the network connections for some VTEs can become I/O saturated while others are left idle. This problem is especially prevalent in JES3 installations and DLm configurations that have 1000+ tape devices configured.
The DLm Control Center (DCC) uses device selection technology developed for the DTS DASD products to enable load balancing across DLm VTEs. DCC influences the device selection during Allocation. Allocation builds an Eligible Device List (EDL) for the tape request, and DCC uses a load balancing selection algorithm to spread the tape requests between the DLm VTEs.
Note: The Load Balancing facility can be used with DLMALLOC or SMS Tape (MTL) controlled DLms, and in both JES2 and JES3 environments.
When a tape management system (TMS) changes the status of a tape to "scratch", the TMS systems calls an exit that can be used by DCC to intercept the scratch request. DCC can immediately notify the DLm that the tape is now scratch. This allows the DLm to have the scratch status synched real-time with the tape management system. The currently supported TMS systems: IBM RMM.
The EMC DLm devices do not have the concept of read-only tape protection. When physical tapes were common, after a tape was created operators could pull the write-ring to disable future updates. DCC has a facility to write protect tape volumes by manipulating the Read-Only flag on the tape emulation file located on the backend storage device. The flag can be displayed or changed using the the DCC DLMCMD TSO or console command, or manipulated using the DLMOPT keyword on a DD statement or the DLMALLOC rules language to create policies to selectively protect output tapes. When a tape emulation file is marked as read-only, the DLm will not modify the virtual tape. Mainframe users receive the same console and JES messages that would occur when a write-ring is removed.
DCC provides a wide range of benefits that will ultimately allow installations to more effectively install, implement and manage the Disk Library for mainframe (DLm). This will be accomplished by providing:
Robust Command and Monitoring Interface
- Modern, efficient and familiar interface
- ISPF/TSO, GUI, z/OS system console, batch, smartphone
- Capture DLm events via an SNMP or the channel interface
Advanced Intelligent Device Selection
- Advanced Allocation Control ensures proper device selection
- Eliminates the need for JCL changes
- Eliminates the need for OAM or SMS management of DLm tapes
- Provides policies for scratch, multivolume and unit-affinity requests
Efficient Transition via Automated Migration Manager
- Automates and manages the migration of tape libraries
- Unique ‘cloning’ technology for maximum accuracy & effectiveness
- NO updates to TMS required
- Provides simplicity to complex issues
Load Balancing Optimization
- Optimizes performance for multi-VTE DLms
- Automated via a device selection algorithm
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|Apr 23 2013||75.10 MB||54 Minutes|
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“DCC was very easy to install and implement. It makes monitoring and administration of the EMC DLm very easy and much more robust than the EMC provided tools. Being able to have DCC automatically scratch tapes on the DLm is a big advantage over having to run a separate process.”
Large Utility Company
“I’d say DCC was a success! You were correct that it did go quickly once we were able to start the jobs and let them run. The DTS support team were real troopers to get us through some of the internal weirdness we have. Thanks to you all!!!! “
Indiana Farm Bureau Insurance
“I want to say thank you to DTS Software. They were a key vendor in both strategic and tactical roles. Special thanks to the technology resources at DTS. It was the DTS sauce that made the VTL conversation a hit on the data center floor.”
In mid-2008, the DTS distributor in Japan (CLC) requested permission to use ACC to control tape allocation for Bus-Tech MDL migration projects. This led to the discovery that DTS and Bus-Tech shared the same distributor in Japan, and that our offices in Raleigh, NC are located approximately six miles apart. After learning more about the MDL capabilities and the new MDL channel interface being introduced by Bus-Tech in Virtuent 7, DTS started development of MCC in late 2009 using components from existing DTS products. The resulting product far exceeded the initial allocation control product and migration tool envisioned early in the project. DTS released MCC in late 2010.
Note: After EMC purchased Bus-Tech in early 2011, MCC was renamed to "DLm Control Center (DCC)".