VSAM Interview Questions and Answers - DoAnswers.com

Virtual Storage Access Method (VSAM) is an IBM disk file storage scheme first used in the OS/VS2 operating system and later used throughout the MVS architecture. VSAM comprises four access methods: Key Sequenced Data Set (KSDS), Relative Record Data Set (RRDS), Entry Sequenced Data Set (ESDS) and Linear Data Set (LDS). See record-oriented filesystem. VSAM records can be of fixed or variable length. They are organised in fixed-size blocks called Control Intervals (CIs), and then into larger divisions called Control Areas (CAs). Control Interval sizes are measured in bytes � e.g. 4K � while Control Area sizes are measured in disk tracks or cylinders. Virtual Storage Access Method (VSAM) is an IBM disk file storage scheme first used in the OS/VS2 operating system and later used throughout the MVS architecture. VSAM comprises four access methods: Key Sequenced Data Set (KSDS), Relative Record Data Set (RRDS), Entry Sequenced Data Set (ESDS) and Linear Data Set (LDS). See record-oriented filesystem. VSAM records can be of fixed or variable length. They are organised in fixed-size blocks called Control Intervals (CIs), and then into larger divisions called Control Areas (CAs). Control Interval sizes are measured in bytes � e.g. 4K � while Control Area sizes are measured in disk tracks or cylinders. Virtual Storage Access Method (VSAM) is an IBM disk file storage scheme first used in the OS/VS2 operating system and later used throughout the MVS architecture. VSAM comprises four access methods: Key Sequenced Data Set (KSDS), Relative Record Data Set (RRDS), Entry Sequenced Data Set (ESDS) and Linear Data Set (LDS). See record-oriented filesystem. VSAM records can be of fixed or variable length. They are organised in fixed-size blocks called Control Intervals (CIs), and then into larger divisions called Control Areas (CAs). Control Interval sizes are measured in bytes � e.g. 4K � while Control Area sizes are measured in disk tracks or cylinders.

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This information is listed in the report produced by Listcat Entries function of the IDCAMS utility.

13. How can you find out what is the amount of unused space for a specific VSAM cluster ?

Compare Higher allocated RBA with Higher used RBA in the Listcat function listing.

14. How do you calculate record size of an alternate cluster? Give your values for both unique and nonunique.

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

15. How do you calculate record size of an alternate cluster? Give your values for both unique and non-unique.

Unique Case: 5 + ( alt-key-length + primary-key ) Nonunique Case: 5 + ( alt-key-length + n * primary-key )

Actually in my project we are always do like this. we dont need to comiple the module sepertly. While adding to UT stage 1 it will be compiled direclty and will give MAX CC . if we have any errors while compiling then we will modify and agian update to UT stage 1.

You can use RERPO option in IDCAMS utility. Let's be a little more precise.We will take the tack that you will be creating a KSDS file.First, you need to know which field/s you will be using as the primary key and if you need, alternate keys. Sort the records by that field/s.Use IDCAMS REPRO to load the flat file into the VSAM file.

CI size should be based on record length, type of processing. Usually CI is 4K. If record length is larger(>1K), chose 6K or 8K. FREESPACE should be large if more number of insertions are envisaged. Usual values are (20 20) when heavy updates are expected. CI size can be calculated.

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 catlg and also specify space=(trk,0)