VSAM经典面试题.doc

Q42)What is SHAREOPTS ?Q42)SHAREOPTS is a parameter in the DEFINE and specifies how an object can be shared among users. It is coded as SHAREOPTS(a b), where a is the cross region share option ie how two or more jobs on a single system can share the file, while b is the cross system share option ie how two or more jobs on different MVSs can share the file. Usual value is (2 3).SHAREOPTS（Shareoptins） 是在定义VSAM时的一个参数，用来定义在用户之间的共享。他可以写作SHAREOPTS(a b) ,a是访问共享选项表示两个或者两个以上的JOB在单个系统中可以获得该共享，b是作为访问共享选项表示两个或者两个以上的JOB在不同的MVS系统中可以获得该共享，一般定义成（2，3）Q43)What is the meaning of each of the values in SHAREOPTS(2 3)?Q43)Value of 2 for cross region means that the file can be processed simultaneously by multiple users provided only one of them is an updater. Value of 3 for cross system means that any number of jobs can process the file for input or output (VSAM does nothing to ensure integrity).2表示同时能被多个用户处理，但只能有一个用户更新，3表示JOB能处理这个文件做输入输出（但VSAM不保证（文件）的完整性）Q44)How do you define a KSDS ?Q44)DEFINE CLUSTER(cluster name) with the INDEXED parameter. Also specify the ds name for the DATA component & the ds INDEX component. Other important parms are RECORDSIZE, KEYS, SHAREOPTIONS.用DEFINE CLUSTER来定义索引的参数，同时定义DS名字在DATA部和INDEX部，其他重要的参数有RECORDSIZE, KEYS, SHAREOPTIONS.Q45)How do you define an ALTINDX ? How do you use ALTINDXs in batch, CICS pgms ?Q45)DEFINE ALTERNATEINDEX. Important paramters are RELATE where you specify the base cluster name, KEYS, RECORDSIZE,SHAREOPTIONS,UNIQUEKEY(or NONUNIQUEKEY), DATA(ds name for the data component), INDEX(ds name for the index component). Then DEFINE PATH. Important paramters are NAME (ds name for the path), PATHENTRY (ds name of the alternate index name), UPDATE(or NOUPDATE) which specifies whether an alt index is updated when a update to the base cluster takes place. Then BLDINDEX. Parameters are INDATASET(ds name of base cluster), OUTDATASET(ds name of AIX).如何定义一个次键？定义次键的主要参数有RELATE，用来关联主键的cluster名，KEYS, RECORDSIZE,SHAREOPTIONS,UNIQUEKEY(or NONUNIQUEKEY), DATA(数据部), INDEX(索引部)。接着定义路径，重要的参数有NAME（路径名），PATHENTRY（索引部的别名），UPDATE(or NOUPDATE)用来定义是否根据主键改变而改变。最后一个过程BLDINDEX（在索引中装入数据）他的参数又INDATASET(主键的ds名), OUTDATASET(次键的ds名 ).Q46)Using Alternate Indexes in Batch pgms:Q46)In the JCL, you must have DD stmts for the cluster and for the path(s). In the COBOL Program, SELECT . ASSIGN TO ddname for base cluster RECORD KEY IS. ALTERNATE RECORD KEY IS. 在jcl中，通过dd参数来指定cluster的路径，在cobol中用SELECT . ASSIGN TO ddname for base cluster RECORD KEY IS. ALTERNATE RECORD KEY IS.Q47)Using Alternate Indexes in CICS pgms:Q47)FCT entries must be created for both base cluster & the path. To read using the alternate index, use the dd name of the path in CICS file control commands.（学完后补充）Q48)What happens when you open an empty VSAM file in a COBOL program for input?Q48)A VSAM file that has never contained a record is treated as unavailable. Attempting to open for input will fail. An empty file can be opened for output only. When you open for output, COBOL will write a dummy record to the file & then delete it out.在COBOL程序中你输入一个空的VSAM文件时会发生什么？VSAM文件不会包含无效的记录，所以打开一个空的VSAM作为（COBOL的）输入文件会失败，空的VSAM文件只能作为输出文件。当你作为输出文件打开的时候COBOL会写一个空的记录在文件中，然后删除。Q49)How do you initialize a VSAM file before any operation? a VSAM with alternate index?Q49)Can write a dummy program that just opens the file for output and then closes it. 你如何初始化一个vsam文件在所有操作之前?一个有次键的vsam？写一个输入空数据的程序，然后关闭它。Q50)What does a file status of 02 on a VSAM indicate?Q50)Duplicate alternate key . Happens on both input and output operationVSAM文件状态是02说明什么？在输入和输出的时候，对索引文件成功但发现了重复关键字Q51)How do you calculate record size of an alternate cluster? Give your values for both unique and nonunique.Q51)Unique Case: 5 + (alt-key-length + primary-key)Non unique Case: 5 + (alt-key-length + n * primary-key) where n = number of duplicate records for the alternate key怎么计算次键的记录长度？给出次键唯一和不唯一情况下的值。唯一： 5 + ( alt-key-length + primary-key )不唯一：5 + ( alt-key-length + n * primary-key ) n为次键重复的个数。原文补充：. A key sequenced base cluster（KSDS）RECSZ = 5 + AIXKL + (n x BCKL). An entry sequenced base cluster（ESDS）RECSZ = 5 + AIXKL + (n x 4)where: RECSZ is the average record size. AIXKL is the alternate-key length (see the KEYS parameter). BCKL is the base clusters prime-key length (you can issue the accessMethod services LISTCAT command to determine the base clustersprime-key length). n = 1 when UNIQUEKEY is specified (RECSZ is also the maximum recordsize). n = the number of data records in the base cluster that contain the samealternate-key value, when NONUNIQUEKEY is specified.Q52)What is the difference between sequential files and ESDS files?Q52)Sequential (QSAM) files can be created on tape while ESDS files cannot. Also, you can have ALTINDEX for an ESDS while no such facility exists for QSAM files.顺序文件（SDS）和ESDS有什么不同？QSAM指的是顺序的文件访问方式。顺序文件可以建立在磁带上，你可以为ESDS定义次键，而QSAM文件不行。Q53)How do you load a VSAM data set with records?Q53)Using the REPRO command. 如何加载VSAM数据集记录，用IDCAMS的REPRO命令。Q54)How do you define a GDG ?Q54)Use the DEFINE GENERATIONDATAGROUP command. In the same IDCAMS step, another dataset must be defined whose DCB parameters are used when new generations of the GDG are created. This dataset is known as the model dataset. The ds name of this model dataset must be the same as that of the GDG, so use a disp of keep rather than catalog and also specify space=(trk,0)如何定义GDG用（IDCAMS）的DEFINE GDG命令，在同一IDCAMS步中，当新的GDG世代新建的时候，必须定义DCB参数。这个数据是被称为模型,模型的名字必须和GDG名字一样。用DISP来定义新的DS。删除和定义GDG：Q55)Do all versions of the GDG have to be of the same record length ?Q55)No, the DCB of the model dataset can be overridden when you allocate new versions.GDG的每一代都需要一样的记录长度吗？不，当新建一代的时候，这个模式（GDG）的DCB（数据控制块）会被覆盖。Q56)How are different versions of GDG named?Q56)base-file-name.GnnnnnV00 where nnnn= generation number (upto 255). nnnn will be 0000 for the 1st generation.GDG如何定义不时代？GnnnnnV00 nnnn是世代号（可到255） 00是版本号，nnnn=0000表示第一代。Q57)Suppose 3 generations of a GDG exist. How would you reference the 1st generation in the JCL? - GSQ57)Use GDG name (-2).假设已经存在3代GDG，在JCL中如何访问第一代？用GDG name(-2).Q58)Suppose a generation of GDG gets created in a particular step of a proc. How would you refer the current generation in a subsequent step? What would be the disposition of this generation now? - GSQ58)Relative generation numbers are updated only at the end of the job, not at the end of a step. To allocate a new generation, we would be using (+1) with a DISP of (NEW, CATLG, DELETE). To refer to this in a subsequent step in the same job, we would again use (+1) but with a DISP of SHR or OLD.如何在一步中建立一代GDG，如何正确的指定一代在随后的一步？如何处理当前的这代？世代号只在结束JOB的时候被更新，而不是JOB中每一步的结束。建立新的世代用（+1）和DISP= (NEW, CATLG, DELETE)，在随后的步中用（+1）和DISP=SHR或OLD来访问新建的这代。Q59)What more info you should give in the DD statement while defining the next generation of a GDG? - GSQ59)Give (+1) as the generation number, give (new,catlg) for disp, give space parameter, can give the DCB parameter if you want to override the dcb of the model dataset.在定义下一代GDG的时候，需要那些DD参数？Q60)Assuming that the DEFINE JCL is not available, how do you get info about a VSAM files organisation?Q60)Use the LISTCAT command.假设不能定义JCL，如何看VSAM 文件的组织结构？用LISTCAT。全部信息：LISTCAT ENTRIES(/) ALLQ61)During processing of a VSAM file, some system error occurs and it is subsequently unusable. What do you do?Q61)Run VERIFY. 在处理VSAM文件的时候，如果一些系统错误发生，然后使VSAM文件无效了，怎么办？运行VERIFY参数（IDCAMS参数）。Q62)How do you fix the problem associated with VSAM out of space condition? Q62)Define new VSAM dataset allocated with more space.Use IDCAMS to REPRO the old VSAM file to new VSAM dataset. Use IDCAMS to ALTER / rename the old VSAM dataset or se IDCAMS to DELETE the old VSAM dataset. Use IDCAMS to ALTER / rename the new VSAM dataset to the name of the original VSAM dataset. 如何解决VSAM空间不够的情况？定义一个更大的新的VSAM数据集。用IDCAMS的REPRO把旧VSAM文件考到新的VSAM文件中。用IDCAMS的ALTER重命名旧的VSAM文件或者用IDCAMS的DELETE删除旧的VSAM文件。用IDCAMS的ALTER重命名新的VSAM文件和原来的（旧的）一样。Q63)What is the meaning of VSAM RETURN-CODE 28? Q63)Out of space condition is raised. VSAM的返回码为28什么意思？命令超出了空间。补充：28是一个I/O的错误，Data set cannot be extended because VSAM cannot allocate additional direct-access storage space. Either there is not enough space left to make the secondary allocation request, youattempted to increase the size of a data set while processing with SHROPT=4 and DISP=SHR, orthe index CI is not large enough to hold the entire CA. This error could also be due to a data set trying to extend beyond 4GB on a system that does not support extended addressability.Q64)On which datasets You can have ALT INDEX?.Q64)only on KSDS and ESDS - not RRDS在那些DS上你可以建立次键KSDS和ESDS。Q65)How many Alternate Indexes you can have on a dataset? Q65)255 - but you must be a nut to have so many ALT Indexes on a dataset!在一个DS中可以定义多少个次键？255，但是你必须要有足够的ALT IndexesQ66)Is it slower if you access a record through ALT INDEX as compared to Primary INDEX?Q66)Yes. Why? Because the alternate key would first locate the primary key, which in turn locates the actual record. Needs twice the number of I/Os.访问记录通过次键相比通过主键要慢？是，因为次键会先寻找主键，从而找到实际记录。Q67)What is RECOVERY and SPEED parameters in DEFINE CLUSTER command?Q67)RECOVERY (default) and SPEED are mutually exclusive. Recovery preformats the control areas during the initial dataset load, if the job fails, you can restart but you must have a recovery routine already written to restart the job. SPEED does not preformat the CAs. It is recommended that you specify SPEED to speed up your initial data load. 在DEFINE CLUSTER命令中 RECOVERY 和 SPEED 是什么？RECOVERY（默认）和SPEED是相对的，Recovery在初始化的时候先加载CA，如果JOB运行失败，你可以重新运行，但是你必须要确保recovery的例程去重启这个JOB，SPEED不预先加载CA，它被推荐用作加快你的初始化。Q68)Describe SHAREOPTIONS parameter (SHR) in Define Cluster command.Q68)It defines the cross-region and cross-system sharing capabilities of the dataset. Syntax is SHR(Crvalue, CSvalue) value 1 means multiple read OR single write (read integrity) 2 means multiple read AND single write (Write integrity) 3 means Multiple read AND multiple write 4 is same as 3, which refreshes the buffer with every random access. default is SHR(1 3).描述下SHAREOPTIONS参数当设置SHAREOPTIONS (1,x)时，系统允许一个用户对VSAM数据集进行读写操作，或者允许多个用户进行读操作。如果有一个用户已经进行读写操作了，那么后面申请读操作的用户会得到失败的反馈。这种情况下VSAM维护数据的完整性。当设置SHAREOPTIONS (2,x)时，系统允许一个用户进行读写，同时允许多个用户进行读操作。当已经有一个用户正在写入时，允许其他用户读入VSAM数据集，但是不允许其他人进行写了。而SHAREOPTIONS (3,x)则允许多个用户同时进行读写操作。4和3一样。默认是1 3Q69)What does the KEYRANGES parameter in Define Cluster commend do?A69)It divides a large dataset into several volumes according to the Key ranges specified. e.g., KEYRANGES (0000001 2999999) (3000000 5999999). if the activity on the key ranges are evenly distributed, concurrent access is possible, which is a performance improvement.Define Cluster中的KEYRANGES是用来干嘛的？根据KEYRANGES的定义来把大DS分配到数个磁盘卷中。比如定义KEYRANGES (0000001 2999999) (3000000 5999999)，如果KEY被分配在这个范围内，可以执行并行访问。补充：The maximum number of key ranges for an alternate index is 123.如果KEYRANGES定义的值比正式的要短，它会在右边补0Q70)What are the optional parameters to the input dataset While loading the empty cluster with the data records? A70)1)FROMADDRESS(address) 2)TOADDRESS(address) where address specifies the RBA value of the key of the input record. 3)FROMNUMBER(rrn) 4)TONUMBER(rrn) where rrn specifies the relative record number of the RRDS record 5)FROMKEY(key) 6)TOKEY(key) where key specifies the key of the input record 7)SKIP(number) 8)COUNT(number) where number specifies the number of records to skip or copy Ex: REPRO INFILE(DD1) OUTFILE(DD2) SKIP(9000) COUNT(700) - Skips the first 9000 records and begins copying at 9001 and copies 700 records from DD1 to DD2. 什么操作可以往一个空的CLUSTER加载数据记录？当地址定义为key值的RBA记录时用1)FROMADDRESS(address) 2)TOADDRESS(address)当定义为RRDS记录时用3)FROMNUMBER(rrn) 4)TONUMBER(rrn)当定义KEY的记录时候用5)FROMKEY(key) 6)TOKEY(key)7)SKIP(number) 8)COUNT(number)用来跳过记录或者打印记录例REPRO INFILE(DD1) OUTFILE(DD2) SKIP(9000) COUNT(700)中把dd1的数据拷贝到dd2中那么他将跳过前9000条数据，接着拷贝700条记录。Q71)What is IDCAMS? and what is the purpose of it?.A71)IDCAMS is an access method services utility used for creating, deleting, altering VSAM files and copying sequential file to a VSAM file, etc.什么是IDCAMS，用它的目的是什么？IDCAMS是 access method services utility 他被用作建立，删除，修改VSAM文件和复制顺序文件和VSAM文件，等等。Q72)How to delete a member using JCL.A72)Using IDCAMS a member can be deleted. DELETE XXX.YYY(member) 如何用JCL删除member用IDCAMS的DELETE XXX.YYY(member)Q73)What is the Difference between LDS & ESDS ?A73)These two datasets are VSAM datasets. ESDS maintains control information. But LDS does not maintains the control information.LDS和ESDS有什么不同?这两个都是VSAM数据集，ESDS有维护控制信息，但LDS没有。（LDS其实就是放置大数据用的）Q74)Is a delete operation possible in an ESDS?B. Is rewrite operation possible in ESDS ?A74)No delete operation is not possible in VSAM ESDS.B. Yes rewrite operation is possible in an ESDS.ESDS可以做删除操作么？在ESDS中可以作复写操作吗？不能删除记录在ESDS，可以复写。Q75)What is an alternate index