LOCKS - Reading Block Dumps

From: Larry Elkins <elkinsl_at_flash.net>
Date: Tue, 04 Dec 2001 09:46:34 -0800
Message-ID: <F001.003D4CB4.20011204093625@fatcity.com>

Listers,

Playing around with dumping a block to determine rows which are locked. I did an update to a single row in a table and did not commit. I dumped the block. Here is the relevant info:

tab 0, row 0, @0x19c3
tl: 21 fb: --H-FL-- lb: 0x1 cc: 3

After rolling back and dumping the block, I get the following:

tab 0, row 0, @0x1977
tl: 27 fb: --H-FL-- lb: 0x0 cc: 3

It looks like to me that the "lb:" value indicates the presence of a lock on the row -- 0x1 for a lock, 0x0 for not locked. I've been googling for a bit, searching usenet, and the typical web sites for info on this and came up empty handed. So, can anyone confirm this idea of lb: 0x0 meaning no lock and 0x1 meaning the row is locked?

Also, there seems to be some differences in the block header info related to ITL's:

Lock present:

 Itl           Xid                  Uba         Flag  Lck        Scn/Fsc

0x01 xid: 0x0002.018.00000482 uba: 0x0080c4a8.0340.0e ---- 1 fsc 0x0006.00000000

No lock:

 Itl           Xid                  Uba         Flag  Lck        Scn/Fsc

0x01 xid: 0x0001.037.000004c3 uba: 0x00800107.06dc.31 C--- 0 scn 0x0000.00594c1b

Can I assume that Scn/Fsc value of non-zero means there is a lock? And last but not least, any good info anywhere on reading block dumps?

Regards,

Larry G. Elkins
elkinsl_at_flash.net
214.954.1781

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Author: Larry Elkins
INET: elkinsl_at_flash.net

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