2 data buffers by default for ESDS. For KSDS it allots 2 data buffers and 1 index buffers. each buffer is about 4k.
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An alternate index is an another way of accessing key sequenced data record stored in a base cluster and path is the linkage which connect alternate index to its base cluster.
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No delete operation is not possible in VSAM ESDS.B. Yes rewrite operation is possible in an ESDS.
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These two datasets are VSAM datasets. ESDS maintains control information. But LDS does not maintains the control information.
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Using IDCAMS a member can be deleted. DELETE ‘XXX.YYY(member)
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IDCAMS is an access method services utility used for creating, deleting, altering VSAM files and copying sequential file to a VSAM file, etc.
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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.
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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.
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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).
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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.
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