IBM SG24-5360-00 manual What Is an IBM Ramac Virtual Array?, Log Structured File

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Chapter 1. The IBM RAMAC Virtual Array

In this chapter we describe the RAMAC Virtual Array (RVA) and the support that VSE/ESA delivers for it.

1.1 What Is an IBM RAMAC Virtual Array?

We explain functions here on a level that is needed to understand how data is stored and organized on an RVA. If you would like more detailed descriptions of this interesting virtual disk architecture, see the redbook entitled IBM RAMAC Virtual Array, SG24-4951.

1.1.1 Overview of RVA and the Virtual Disk Architecture

Traditional storage subsystems such as the 3990 and 3390 use the count key data (CKD) architecture. The CKD architecture defines how and where on the disk device the data is physically stored. Any updates to the data are written directly to the same position on the physical disk from which the updated data was read. This is referred to as update in place.

IBMs RVA provides a high-availability, high-performance storage solution thanks to its revolutionary virtual disk architecture. To the host, the RVA appears as up to four traditional 3990 storage controls, with up to 256 3380 or 3390 volumesÐ64 functional volumes on each 3990. These devices do not physically exist in the subsystem and are referred to as functional devices. Physically, the subsystem contains RAID 6-protected arrays of fixed block architecture (FBA) disk devices.

1.1.2 Log Structured File

The RAID-protected FBA disk arrays that make up the RVAs physical disk space are sequentially filled with data. New and updated data is placed at the end of the file, as it is on a sequential or log file. We call this architecture a log structured file.

Updates leave areas in the log file that are no longer needed. A microcode process called freespace collection ensures that these areas are put back so that there is always enough freespace for writing. This process runs as a background task. You can control the freespace by observing the net capacity load (NCL) of the RVA and using the IBM Extended Facilities Product (IXFP) program. See the RVA redbook entitled IBM RAMAC Virtual Array for more information. The RVAs physical disk space typically should be kept below 75% NCL. Above that level, the freespace collection process runs with higher priority, and performance degradation may result. A service information message (SIM) informs operators when this threshold is reached.

The following tables are used to map the tracks of functional devices to the FBA blocks related to those tracks:

Functional device table

The functional device table (FDT) holds the information about the functional volumes that have been defined to the RVA.

Functional track directory

© Copyright IBM Corp. 1999

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Contents International Technical Support Organization Page International Technical Support Organization First Edition January Contents Peer-to-Peer Remote Copy Itso Redbook Evaluation Contents Vi Ramac Virtual Array, Peer-to Peer Remote VSE/ESA Team That Wrote This Redbook PrefaceYour comments are important to us Comments WelcomeLog Structured File What Is an IBM Ramac Virtual Array?IBM Ramac Virtual Array Overview of RVA and the Virtual Disk Architecture− Functional track table Data Compression and CompactionVSE/ESA Support for the RVA What Is IXFP/SnapShot for VSE/ESA?What Is SnapShot? Deleted Data Space Release What Is IXFP?Reporting Functions What Is Peer-to-Peer Remote Copy?Ramac Virtual Array, Peer-to Peer Remote VSE/ESA Disk Capacity RVA Benefits for VSE/ESARVA Simplifies Your Storage Management Batch Window Improvement AdministrationIxfp IXFP/SnapShot for VSE/ESA Ramac Virtual ArrayHardware Application DevelopmentRVA Data Availability Pprc SnapShotRamac Virtual Array, Peer-to Peer Remote VSE/ESA Prerequisites VSE/ESA Support for the RVAHost Connection Volumes1 VSE/ESA Input/Output Configuration Program Exec Volume Minimal InitPartial Disk Minimal Init AssgnRamac Virtual Array, Peer-to Peer Remote VSE/ESA System VSE/ESA User Time IXFP/SnapShot for VSE/ESASample Batch Job to Invoke Ixfp Report Function DTRIATTN,PARM=′ Ixfp REPORT′IXFP/SnapShot for VSE/ESA Defined DetailPhys AR 0015 CUU DEFIxfp Snap Full VolumeVSE/VSAM Reply ′ YES′ to ProceedRange of Cylinders Non-VSAM File Expired Files Ixfp DDSR,PATEV30000-0999,NOPROMPT Total VolumeIxfp DDSR,PATEV3 Ixfp DDSR,PATEV3DSN=′ test.data.3′ , Noprompt Specified FileIxfp Report Ixfp REPORT,80E Ixfp REPORT,80FIxfp REPORT,80E,80F Device Detail Report Sample Output of Ixfp Report CommandRamac Virtual Array, Peer-to Peer Remote VSE/ESA Subsystem Summary Report Device Summary ReportRamac Virtual Array, Peer-to Peer Remote VSE/ESA Peer-to-Peer Remote Copy Peer-to-Peer Remote CopyPprc Data Flow Pprc and VSE/ESA Software RequirementsInvoking peer-to-peer remote copy Pprc Hardware RequirementsSecondary Devices of a Pprc Pair Examples of Pprcopy CommandsSnapShot Considerations Primary Devices of a Pprc PairRecovering from a Primary Site Failure Setting Up Pprc Paths and PairsPhysical Connections to the RVA Recovering from a Secondary Site FailureDeleting Pprc Pairs and Paths Determining the Channel Connection Address Determining the Logical Control Unit Number for RVARamac Virtual Array, Peer-to Peer Remote VSE/ESA Functional Device Configuration Appendix A. RVA Functional Device ConfigurationFunctional Device Configuration Screen CD23 Syntax Appendix B. Ixfp Command ExamplesSnap Command Ramac Virtual Array, Peer-to Peer Remote VSE/ESA Noprompt Using SnapShot to Copy One Volume to AnotherTest Prod Overall Test Prod AR 0015 CapacityDEFINED-CAPACITY Using SnapShot to Copy Files with Relocation Using SnapShot to Copy a File from One Volume to AnotherIXFP20I Snap Function Completed AT Other Uses of SnapShotSyntax of Ixfp Ddsr Command Details Ddsr CommandUsing Ddsr to Delete the Contents of a Volume Using Ddsr to Delete a Single Data SetAR+0015 IXFP29D Ddsr for For Deletion Using Ddsr to Delete the Free Space on an RVAReport Report Command Device Detail Report FUNC. Capacity MB Reporting on the Capacity of a Single VolumeReporting on the Capacity of Multiple Volumes Reporting on the Capacity of the RVA SubsystemExec DTRIATTN,PARM=′ Ixfp REPORT′ IXFP/SnapShot Setup Job StreamsJOB WCWTEST1 Ready Ixfp DDSR,80F BG 0000 // JOB InitdiskBG 0000 1A86I Following Assignments are Released Ixfp DDSR,80E$$DITTO BLKFACTOR=1 EOJ 50.83 47.86 AR 0015 1I40I Ready$$DITTO BLKFACTOR=1 $$DITTO EOJ 726532.208 MB 117880.209 MB 57754.953 MB Appendix C. VSE/VSAM Considerations Backing up Vsam Volumes Appendix C. VSE/VSAM Considerations Ramac Virtual Array, Peer-to Peer Remote VSE/ESA Appendix D. Iocds Example Ramac Virtual Array, Peer-to Peer Remote VSE/ESA Appendix E. Special Notices Following terms are trademarks of other companies Other Publications Appendix F. Related PublicationsInternational Technical Support Organization Publications Redbooks on CD-ROMsRamac Virtual Array, Peer-to Peer Remote VSE/ESA ∙ E-mail Orders How to Get Itso RedbooksPlease send me the following IBM Redbook Fax Order FormSee CKD IndexPprc distance Please answer the following questions Itso Redbook EvaluationSG24-5360-00