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nartcr
New User
Joined: 06 Jun 2007
Posts: 83
Location: anada
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Hello,
I am learning Natural and Adabas through manuals.. There is something i do not understand from the manuals,and i am trying to find the answer in Vain. Its regd how a data is stored in Adabas.
I took the below table from Adabas documentation. If you notice the ISN 10, ISN 11 and ISN 12, it resides on same block number, but it contains different data. I was under the impression that ISN would be unique for the data record until it is reassigned or when data gets deleted. Would you be able to examine the below table -- blk size 237, and let me know how same ISN would be used by ADABAS for storing different datarecord. And possibly what would address convertor contain in such case?
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Blk ISN PER-ID FIRST-NM LST-NAME DEPT BIRTH
234 1 11400316 WILLI BEUSE MARK29 390509
234 2 11400314 ERHARD BECKER SALE47 540707
234 13 11300307 JAN KAMAL SALE37 590328
235 4 11400312 INGRID SCHMID MARK19 540308
235 5 11400310 MARGAR GROTH MARK29 540623
235 6 11400307 JOSEFA LEYRER COMP28 410407
236 7 11400304 MARIAN RACKMAN COMP28 541209
236 9 11300319 SULEYM YALCIN SALE37 580819
237 10 11300316 GABRIEL KANTE SALE47 540809
237 11 11300315 GUDRUN FRIESE SALE37 560504
237 12 11300314 GITTA MOHRD SALE17 390912
298 8 11400303 MARTIN WALLIN COMP28 460921 |
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Garry Carroll
Senior Member
Joined: 08 May 2006
Posts: 1193
Location: Dublin, Ireland
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The ISN in all cases shown is unique. It's the BLK that is the same and, in this case, it looks like a block can accommodate three records and BLK 234 has had record 3 replaced by record 13. Record 8 is, for some reason, in an out-of-sequence block.
Garry. |
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nartcr
New User
Joined: 06 Jun 2007
Posts: 83
Location: anada
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| Thanks Gary, I realised that when i copied the table into my word, it rearranged itself making ISN out of sequence ( BLK Size came on ISN column and ISN went into BLKSIZE column ). Thanks a lot. |
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Ralph Zbrog
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Joined: 21 Nov 2009
Posts: 58
Location: California
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ISN is a unique identifier for a record within a file. A record's ISN does not change. But let's say that I add Ralph to my customer file, and Adabas assigns ISN 7. Someone deletes customer Ralph, but I wish to reinstate him. When I add Ralph a second time, there is no reason for me to believe that ISN 7 will be assigned again. As far as Adabas is concerned, two unique records have been created.
During initial load of a file, ISNs will be assigned sequentially. Otherwise ISN assignment is dependent upon Adabas file settings. Unless the data records are quite large, multiple records will fit into each block. During initial load of a file, records are loaded into sequential blocks. Otherwise block assignment is dependent upon Adabas file settings. For various reasons, over time a record may migrate from one block to another.
In the example given, ISN 8 migrated from block 236 to 298. ISN 3 either migrated or was deleted, and its space in block 234 was re-used by ISN 13. |
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