IDS Forum

Re: Differences in RSAM page structure 32 and 64 b

Posted By: JACOB SALOMON
Date: Thursday, 25 January 2018, at 8:00 p.m.

In Response To: Re: Differences in RSAM page structure 32 and 64 b (JACOB SALOMON)

Aha! I have NOT given up!

I managed to recompile my pgdump on my Linux box (A lot goes haywire in 2 decades) and here is a a little bit of the dump of a page in a DBspace with 16-k pages. It happens to be chunk number 6.
pgdump -d /ifmxdev/js_server.data_dbs.P.001 -p 54 -fx -n 1 -s 16

The chunk file is /ifmxdev/js_server.data_dbs.P.001 and I want to dump 1 page starting at page 54 of the chunk. Here is the first few lines of the output:

Device: </ifmxdev/js_server.data_dbs.P.001>; Page <0054/0x0036>; OnLine Page ID: <432/0>
-----------------------------------------------------------------
0000/0000||B0010000 060034E6 7A38B080 3A19F425 |~~~~~~4~z8~~:~~%|
0016/0010||00000000 00000000 09737973 7461626C |~~~~~~~~~systabl|
0032/0020||6573696E 666F726D 69782020 20202020 |esinformix |
0048/0030||20202020 20202020 20202020 20202020 | |
0064/0040||20200000 0301000A 73797363 6F6C756D | ~~~~~~syscolum|
0080/0050||6E73696E 666F726D 69782020 20202020 |nsinformix |
0096/0060||20202020 20202020 20202020 20202020 | |
0112/0070||20200000 0302000A 73797369 6E646963 | ~~~~~~sysindic|

This happens to be the first page in systables for my stores_demo database.

OK, that first word: B0010000 This is actually 0x'000001b0' or just 1b0. Back into decimal this is 432 but divide by 8 (the multiple over the default page size) and you get back the 54 you specified.

In the next word, the chunk number is 0006 - that is Chunk 6, exactly as I specified. What that E634 is? Maybe is only 34 or decimal 52 but I believe I counted 62 slots in the slot table so that makes no sense.

Furthermore I can see that the slot table starts at offset 3E14 and the last row in the page ends about offset 193A. And that I find in the last word of the top line: 3A19F425 There is the 193A in the first 2 bytes of the word. (Intel is little-endian.) I would presume than that the 25F4 is the free count, or 9716. But that does not work out; the full page dump told be there were 589 * 16 bytes of all 0, which comes out to 9524

Since the last 2 words of the page header are pointers to other pages (in the tblspace), in this case no further pages, now I'd like to gain that understanding of what all those other hex number all mean. Someplace is the number of slots in the slot table so I should see 3E someplace.

And the page type is buried in there someplace, in a location other than where it was in the 32-bit version.

So who will take me up on this journey of discovery?

Messages In This Thread

• Differences in RSAM page structure 32 and 64 bit I
  JACOB SALOMON -- Tuesday, 29 July 2014, at 7:25 p.m.
  • Re: Differences in RSAM page structure 32 and 64 b
    Marco Greco -- Wednesday, 30 July 2014, at 4:10 a.m.
    • Re: Differences in RSAM page structure 32 and 64 b
      JACOB SALOMON -- Friday, 16 January 2015, at 10:38 a.m.
      • Re: Differences in RSAM page structure 32 and 64 b
        Madison Pruet -- Friday, 16 January 2015, at 1:32 p.m.
      • Re: Differences in RSAM page structure 32 and 64 b
        JACOB SALOMON -- Thursday, 25 January 2018, at 8:00 p.m.
        • Re: Differences in RSAM page structure 32 and 64 b
          JACOB SALOMON -- Wednesday, 7 February 2018, at 4:11 p.m.

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