Data set structure
數(shù)據(jù)集的結(jié)構(gòu)
Working with data sets requires an understanding of the physical and logical structure of a data set, and how z/OS® accesses information in the data set.
使用數(shù)據(jù)集需要我們理解數(shù)據(jù)集的物理和邏輯結(jié)構(gòu)和Z/OS如果訪問(wèn)這些數(shù)據(jù)集的信息.
Data set
In z/OS, a data set is a named collection of related data records that is stored and retrieved by an assigned name. A data set is equivalent to a file in other operating systems. Data sets are stored on tape or disks.
數(shù)據(jù)集
在Z/OS中,數(shù)據(jù)集是一個(gè)已命名的內(nèi)容相關(guān)數(shù)據(jù)記錄的集合,系統(tǒng)通過(guò)這個(gè)名字保存和訪問(wèn)這些數(shù)據(jù)記錄.數(shù)據(jù)集相當(dāng)于其他操作系統(tǒng)里面的文件.數(shù)據(jù)集是存儲(chǔ)在磁盤(pán)或者是磁帶里面的.
Direct Access Storage Device (DASD)
DASD is another name for a disk drive. Additional synonyms include: disk volume, disk pack, or Head Disk Assembly (HDA).
(DASD)直接訪問(wèn)存儲(chǔ)器
DASD 是磁盤(pán)設(shè)備的別名,它還有其他的同義詞disk volume, disk pack, or Head Disk Assembly (HDA).
Space
Disk space is allocated in units called cylinders, tracks, or blocks.
磁盤(pán)空間
磁盤(pán)空間以柱面,磁道,或者塊為單位作分配.
Cylinder
A disk drive contains cylinders. A cylinder is a unit of storage on a count-key-data (CKD) device with a fixed number of tracks.
柱面
磁盤(pán)包含柱面,一個(gè)柱面是一個(gè)(CKD)設(shè)備上一個(gè)存儲(chǔ)單位,指向一個(gè)固定號(hào)碼的磁道.
Track
Cylinders contain tracks, which are circular paths on the surface of a disk or diskette on which information is magnetically recorded and from which recorded information is read. Tracks are in count-key-data (CKD) format, which means that each track contains fields that indicate the start of the track and the space used, followed by records containing three fields:
• The count field defines the length of the record
• The key field contains optional accounting information
• The data field contains the user data
磁道
柱面包含磁道,它是磁盤(pán)表面的環(huán)形軌道,以磁性物質(zhì)保存和被訪問(wèn)數(shù)據(jù)信息. 磁道使用(CKD)格式,意味著每一個(gè)磁道包含一系列的字段,這些字段指明了磁道的開(kāi)始位置和所用的空間,后面跟隨著數(shù)據(jù)記錄,數(shù)據(jù)記錄內(nèi)保存三個(gè)字段,
.記數(shù)字段包含了記錄的長(zhǎng)度
.關(guān)鍵字字段包含了可選的帳戶(hù)信息
.數(shù)據(jù)字段包含了用戶(hù)的實(shí)際數(shù)據(jù)
Count Key Data（CKD）是一種磁盤(pán)數(shù)據(jù)結(jié)構(gòu)。每條物理磁盤(pán)記錄包含一個(gè)count區(qū)，一個(gè)可選的key，以及在一個(gè)記錄內(nèi)間隔后面的數(shù)據(jù)data記錄。這個(gè)結(jié)構(gòu)后面的原理就是：即然數(shù)據(jù)記錄的長(zhǎng)度可能不同，它們就需要有一個(gè)統(tǒng)計(jì)字段來(lái)指示key和物理記錄的長(zhǎng)度。統(tǒng)計(jì)區(qū)有以柱面頭記錄格式記錄的物理位置標(biāo)識(shí)，Key的長(zhǎng)度，和數(shù)據(jù)記錄的長(zhǎng)度。Key要么沒(méi)有，要么是一串字符。大多數(shù)情況下是沒(méi)有key的，記錄順序排列，或者以直接柱面頭記錄定位。如果有key,則它通常是數(shù)據(jù)記錄前幾個(gè)字節(jié)的拷貝，但它可以是用來(lái)找到這條記錄的任何數(shù)據(jù)。這個(gè)key(還有記錄）都是通過(guò)硬件命令來(lái)定位的。Count Key Data Achitecture是由IBM在20世紀(jì)60年代創(chuàng)建的，用來(lái)作為System/360的磁盤(pán)驅(qū)動(dòng)，也叫固定塊架構(gòu)（Fixed Block Achitecture。
Record
記錄
Tracks contain records. A record is some number of bytes containing data. The record is the basic unit of information used by a program running on z/OS.
磁道包含記錄,一個(gè)記錄是一些包含了數(shù)據(jù)的字節(jié).記錄是Z/OS上應(yīng)用程序處理數(shù)據(jù)的基本單位.
• Records have a logical record length (abbreviated as LRECL); different types of DASD impose different maximum lengths for records.
• Records are either fixed length or variable length in a given data set. Traditional z/OS data sets have one of five record formats (abbreviated as RECFM): Fixed (F), fixed blocked (FB), variable (V), variable blocked (VB), or undefined (U).
.記錄有一個(gè)邏輯記錄長(zhǎng)度(LRECL)屬性,不同的DASD設(shè)備決定了數(shù)據(jù)記錄的最大長(zhǎng)度的不同
.記錄可是定長(zhǎng)的,也可以是變長(zhǎng)的,傳統(tǒng)上,z/OS有5種記錄格式(RECFM),F固定,FB固定,分塊,V變長(zhǎng),VB變長(zhǎng),分塊,U未知
Blocks
Records can be grouped into data blocks, which are the units of recording on disk. Blocking makes processing more efficient because z/OS can access an entire block at once instead of reading or writing records individually.
Block size (abbreviated as BLKSIZE) is the physical block size written on the disk for fixed (F) and fixed block (FB) records. For variable and undefined (V, VB, and U) records, block size is the maximum physical block size that can be used for the data set.
塊
數(shù)據(jù)記錄群組成為數(shù)據(jù)塊,是寫(xiě)入和讀取磁盤(pán)的單位.分塊的方式使數(shù)據(jù)處理更加高效,因?yàn)閦/OS可以用一個(gè)塊的單位來(lái)讀寫(xiě)記錄,而不是一個(gè)一個(gè)記錄單獨(dú)來(lái)讀寫(xiě).
塊大小(BLKSIZE),是指以F(固定)和FB(固定,分塊)格式的數(shù)據(jù)記錄寫(xiě)入磁盤(pán)的塊的大小,對(duì)于分塊,V變長(zhǎng),VB變長(zhǎng),分塊,U格式的數(shù)據(jù)記錄,塊大小是數(shù)據(jù)集最大的可用數(shù)據(jù)物理塊大小.
Extents
擴(kuò)展
Space for a disk data set is assigned in primary and secondary extents. An extent is a contiguous number of disk drive tracks, cylinders, or blocks. Data sets can increase in extents as they grow. As with blocking, the use of extents is more efficient because reading or writing contiguous tracks is faster than reading or writing data that is scattered over the disk.
磁盤(pán)空間分配對(duì)于數(shù)據(jù)集來(lái)說(shuō)包括(primary)第一次分配和二次(secondary)擴(kuò)展,一個(gè)擴(kuò)展分配了一定數(shù)量連續(xù)的磁盤(pán)磁道,柱面,或者塊.基于塊的讀寫(xiě)方式下,使用磁盤(pán)擴(kuò)展數(shù)據(jù)更加高效,應(yīng)為讀寫(xiě)連續(xù)的磁道是比讀寫(xiě)零碎的數(shù)據(jù)快速很多.
Volume
卷
The term volume is often used to refer to a disk.
卷經(jīng)常被認(rèn)為是磁盤(pán)
Volume serial
卷名
The six-character name of a disk or tape volume, such as TEST01.
是磁盤(pán)或者磁帶的名字,6個(gè)字符,例如test01
Device type
設(shè)備類(lèi)型
A model or type of disk device, such as 3390.
磁盤(pán)設(shè)備的型號(hào)或者是類(lèi)型,例如3390
Organization
組織方式
The method of processing a data set, such as sequential.
處理數(shù)據(jù)的方式,例如順序訪問(wèn)