ABCs of z/OS System Programming Volume 3 - IBM Redbooks

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4.32 VSAM: Control interval (CI) LR1 LR2 LRn LR = Logical record RDF = Record definition field CIDF = Control interval definition field LR1 100 bytes LR2 100 bytes LR3 100 bytes Figure 4-42 Control interval format Control interval (CI) The control interval is a concept that is unique to VSAM. A CI is formed by one or several physical records (usually just one). It is the fundamental building block of every VSAM file. A CI is a contiguous area of direct access storage that VSAM uses to store data records and control information that describes the records. A CI is the unit of information that VSAM transfers between the storage device and the main storage during one I/O operation. Whenever a logical record is requested by an application program, the entire CI containing the logical record is read into a VSAM I/O buffer in virtual storage. The desired logical record is then transferred from the VSAM buffer to a user-defined buffer or work area (if in move mode). Based on the CI size, VSAM calculates the best size of the physical block in order to better use the 3390/3380 logical track. The CI size can be from 512 bytes to 32 KB. A CI contents depends on the cluster organization. A KSDS consists of: ► Logical records stored from the beginning to the end of the CI. ► Free space, for data records to be inserted into or lengthened. ► Control information, which is made up of two types of fields: – One control interval definition field (CIDF) per CI. CIDF is a 4-byte field. CIDF contains information about the amount and location of free space in the CI. 162 ABCs of z/OS System Programming Volume 3 Control Interval Format FREE SPACE R D Fn Contigous records of the same size LR4 LRn 150 bytes LR5 100 bytes FREE SPACE R D F4 3 bytes R D F2 R D F1 Control information fields R D F3 R D F2 R D F1 C I D F C I D F 4 bytes
– Several record definition fields (RDF) describing the logical records. RDF is a 3-byte field and describes the length of logical records. For fixed length records there are two RDFs, one with the length, and the other with how many records are the same length. The size of CIs can vary from one component to another, but all the CIs within the data or index component of a particular cluster data set must be of the same length. The CI components and properties may vary, depending on the data set organization. For example, an LDS does not contain CIDFs and RDFs in its CI. All of the bytes in the LDS CI are data bytes. Spanned records Spanned records are logical records that are larger than the CI size. They are needed when the application requires very long logical records. To have spanned records, the file must be defined with the SPANNED attribute at the time it is created. Spanned records are allowed to extend across or “span” control interval boundaries, but not beyond control area limits. The RDFs describe whether the record is spanned or not. A spanned record always begins on a control interval boundary, and fills one or more control intervals within a single control area. A spanned record does not share the CI with any other records; in other words, the free space at the end of the last segment is not filled with the next record. This free space is only used to extend the spanned record. Control area (CA) Control area is also a concept unique to VSAM. A CA is formed by two or more CIs put together into fixed-length contiguous areas of direct access storage. A VSAM data set is composed of one or more CAs. In most cases, a CA is the size of a 3390/3380 cylinder. The minimum size of a CA is one track. The CA size is implicitly defined when you specify the size of a data set at data set definition. CAs are needed to implement the concept of splits. The size of a VSAM file is always a multiple of the CA size and VSAM files are extended in units of CAs. Splits CI splits and CA splits occur as a result of data record insertions (or increasing the length of an already existing record) in KSDS and VRRDS organizations. If a logical record is to be inserted (in key sequence) and there is not enough free space in the CI, the CI is split. Approximately half the records in the CI are transferred to a free CI provided in the CA, and the record to be inserted is placed in the original CI. If there are no free CIs in the CA and a record is to be inserted, a CA split occurs. Half the CIs are sent to the first available CA at the end of the data component. This movement creates free CIs in the original CA, then the record to be inserted causes a CI split. Chapter 4. Storage management software 163
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ibm.com/redbooks Front cover ABCs o
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Note: Before using this information
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3.10 Data sets eligible for EAV vol
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5.5 Implementing SMS policies. . .
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7.29 Accessing a data set with DFSM
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Trademarks IBM, the IBM logo, and i
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Paul Rogers is a Consulting IT Spec
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xiv ABCs of z/OS System Programming
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1.1 Introduction to DFSMS IBM 3494
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Network File System The Network Fil
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Using access methods, commands, and
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Distributed data management DFSMSds
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Shelf management DFSMSrmm groups in
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Availability management DFSMShsm ba
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key functions that enable multiple
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An access method is a DFSMSdfp comp
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including the operating system itse
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2.3 DFSMSdfp data set types Data se
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2.4 Types of VSAM data sets Types o
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Partitioned data set (PDS) Partitio
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► Extended-addressability, which
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method writes data on the first vol
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SMS calculates the average preferen
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Restriction: The following types of
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► REXX LISTDSI function ► CLIST
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Using CLIST OPENFILE INPUT/GETFILE
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2.12 z/OS UNIX files Following are
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Logical records and blocks To an ap
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2.14 Locating an existing data set
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2.15 Uncataloged and cataloged data
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2.17 VTOC and DSCBs VTOC DSCBs Figu
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2.18 VTOC index structure VOLUME LA
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2.19 Initializing a volume using IC
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52 ABCs of z/OS System Programming
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3.1 Traditional DASD capacity 885 C
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Large volume support design conside
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DASD virtual visibility Traditional
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3.4 WLM controlling PAVs zSeries WL
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3.5 Parallel Access Volumes (PAVs)
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3.6 HyperPAV feature for DS8000 ser
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For each z/OS image within the sysp
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Note: With the 3390 Model A, the mo
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Note the following points regarding
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EAS non-eligible data sets An EAS-i
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same as for previous 3390 model dev
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3.13 Using dynamic volume expansion
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3.15 Using Web browser GUI Need a U
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3.17 Increase capacity of volumes F
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3.19 Final capacity increase for vo
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VTOC index changes The index block
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The documentation is in Device Supp
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free space available following the
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Note: The refresh of the index occu
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Updating the VTOC following volume
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USEEAV(YES|NO) YES This means that
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Generally, for VSAM data set alloca
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attributes can reside in the extend
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Other methods for EATTR specificati
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3.30 Migration assistance tracker T
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3.31 Migration tracker commands SET
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4.1 Overview of DFSMSdfp utilities
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4.2 IEBCOMPR utility Example 1 Exam
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Page 130 and 131: 4.4 IEBCOPY: Copy operation DATA.SE
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Page 134 and 135: Copying to z/OS UNIX IEBGENER can b
Page 136 and 137: 4.8 IEBGENER: Copying data to tape
Page 138 and 139: 4.10 IEHLIST LISTVTOC output CONTEN
Page 140 and 141: Examples of IEHINITT In the example
Page 142 and 143: 4.13 DFSMSdfp access methods DFSMSd
Page 144 and 145: physical blocks. QSAM also guarante
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Page 148 and 149: Command Functions DEFINE PAGESPACE
Page 150 and 151: Note: These commands cannot be used
Page 152 and 153: ► Capacity planning: Capacity pla
Page 154 and 155: A GDS has sequentially ordered abso
Page 156 and 157: The parameters are: NAME This speci
Page 158 and 159: 4.21 Relative generation numbers A.
Page 160 and 161: 4.23 PDS data set organization Adva
Page 162 and 163: 4.24 Partitioned data set extended
Page 164 and 165: 4.25 PDSE enhancements PDSE, two ad
Page 166 and 167: 4.26 PDSE: Conversion Using DFSMSds
Page 168 and 169: 4.27 Program objects in a PDSE Func
Page 170 and 171: 4.28 Sequential access methods Sequ
Page 172 and 173: 4.29 z/OS V1R9 QSAM - BSAM enhancem
Page 174 and 175: 4.30 Virtual storage access method
Page 176 and 177: 4.31 VSAM terminology Logical recor
Page 180 and 181: 4.33 VSAM data set components Clust
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Page 192 and 193: 4.43 VSAM resource pool VSAM resour
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Page 200 and 201: 4.47 VSAM SMB enhancement with z/OS
Page 202 and 203: 4.48 VSAM enhancements Data compres
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Page 216 and 217: When to use logical processing Use
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Page 222 and 223: Tasks for availability management f
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DATASSETSIZE(dssize) This specifies
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► Utilize OVERFLOW volumes for mi
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Before automatic secondary space ma
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For data sets larger than 58 K trac
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► Migration level 1 (ML1) volumes
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value of a user-specified RETPD or
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The second-newest version is treate
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If the version has a specified rete
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ACS routines For both automatic and
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- System-managed automated tape lib
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4.75 What DFSMSrmm can manage Remov
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You can also use the DFSMSrmm built
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z/OS V1R8 enhancements DFSMSrmm hel
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5.1 Storage management ISMF dss Fig
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5.3 Goals and benefits of system-ma
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Improved data availability manageme
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► Whether data sets are to be kep
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When the ACS routines are started a
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5.7 Assigning data to be system-man
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Even though data class is optional,
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You can use the ACCESSIBILITY attri
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If you do not explicitly assign a m
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5.12 Using storage groups DFSMShsm-
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5.13 Using aggregate backup and rec
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5.14 Automatic Class Selection (ACS
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5.15 SMS configuration An SMS confi
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5.16 SMS control data sets SMS Figu
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5.17 Implementing DFSMS Enabling th
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► Gain experience with the operat
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Specify SHAREOPTIONS(3,3) for the A
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Defining the SMS base configuration
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5.21 Creating ACS routines Storage
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5.22 DFSMS setup for z/OS IEASYSxx
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5.23 Starting SMS and activating a
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5.24 Control SMS processing with op
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5.25 Displaying the SMS configurati
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exception. If it is clear that a PD
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sets (see Figure 5-27 on page 287).
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Using a high level qualifier (HLQ)
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5.30 Establishing installation stan
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5.32 Data class attributes Data cla
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5.34 Simplifying JCL use Figure 5-3
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► The AVGREC attribute indicates
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Considerations when specifying spac
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5.38 SMS PDSE support SMS PDSE supp
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5.40 Allocating new PDSEs //ALLOC E
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Production batch refers to data cre
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tape are stored as a tape data set
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5.44 ISMF: Product relationships IS
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5.45 ISMF: What you can do with ISM
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5.46 ISMF: Accessing ISMF Panel Hel
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5.48 ISMF: Obtaining information ab
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5.49 ISMF: Data set option Figure 5
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5.51 ISMF: Management Class option
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5.53 ISMF: Storage Class option Fig
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6.1 Catalogs ICF structure 1 ICF st
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6.2 The basic catalog structure (BC
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6.3 The VSAM volume data set (VVDS)
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6.4 Catalogs by function SYSCAT VOL
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User catalogs The difference betwee
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Multilevel aliases You can augment
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Defining a cataloged data set When
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The example in Figure 6-9 on page 3
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6.8 Using multiple catalogs CATALOG
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If you need to share data sets acro
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► List a user catalog connector i
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Note: When you delete a data set, t
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DELET6 JOB ... //STEP1 EXEC PGM=IDC
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Note: The command will result in er
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You can later recover the backup co
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Aliases to the catalog can be defin
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► Physical errors The records on
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Because APF authorization is establ
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3. Use EXAMINE and DIAGNOSE to ensu
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5. Use REPRO MERGECAT to split the
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The two types of buffer are used to
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Catalog report output This MODIFY c
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Restarting the catalog address spac
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► MODIFY CATALOG,LIST The LIST co
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Recover from performance slow downs
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2. Define or alter your existing ca
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7.1 VSAM share options Share option
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7.2 Base VSAM buffering Three types
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7.3 Base VSAM locking Figure 7-3 Ex
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7.5 VSAM record-level sharing intro
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► Non-CICS jobs can have read-onl
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7.8 Buffering under VSAM RLS CICS R
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7.9 VSAM RLS locking control interv
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7.10 VSAM RLS/CICS data set recover
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7.11 Transactional recovery Commite
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7.13 VSAM RLS implementation Update
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Cache structures Coupling Facility
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7.15 Update PARMLIB with VSAM RLS p
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7.16 Define sharing control data se
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Tip: Place the SHCDSs on separate v
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Command ===> Figure 7-22 CF cache u
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7.18 Update data sets with log para
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7.19 The SMSVSAM address space RLS
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7.20 Interacting with VSAM RLS Inte
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To learn about other DISPLAY comman
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to use this specification or the sp
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► RECOVERY REQUIRED This field in
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DFSMStvs is a follow-on project/cap
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Like CICS, DFSMStvs does not perfor
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It is RRS that provides the means t
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7.27 Unit of work and unit of recov
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► Log of logs (optional, shared w
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7.30 Application considerations Bre
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7.31 DFSMStvs logging implementatio
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LABEL JOB ... //STEP10 EXEC PGM=IXC
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7.33 Update PARMLIB with DFSMStvs p
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7.34 The DFSMStvs instance CICSA R/
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Changes to parameters other than AK
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7.36 Summary Figure 7-48 Summary Ba
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8.1 Overview of DASD types Traditio
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8.2 Redundant array of independent
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8.3 Seascape architecture Powerful
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► Data copy sharing Data copy sha
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NVS cache NVS is used to store a se
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8.6 ESS major components Figure 8-6
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8.8 FICON host adapters FICON host
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8.9 ESS disks Eight-packs Set of 8
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8.10 ESS device adapters SSA 160 De
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8.11 SSA loops SSA operation 4 link
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8.12 RAID-10 RAID-10 configurations
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8.13 Storage balancing with RAID-10
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Peer-to-peer remote copy (PPRC) PPR
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8.15 ESS performance features Prior
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8.16 IBM TotalStorage DS6000 Enterp
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DS6000 expansion enclosure (Model 1
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support for one or two expansion fr
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The DS8300 models can support eithe
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consolidations where separate stora
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Copy Services include the following
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TotalStorage Expert helps storage a
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identifying the data set and descri
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Table 8-4 Types of labels Code Mean
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equired. Therefore, the resulting t
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Drive designed for automation solut
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3494 models and features IBM 3494 o
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Each FICON channel in the VTS can s
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In addition to the 3494 VTS compone
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► Consolidation Another benefit i
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Online resources ► z/OS DFSMShsm
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