[Info-vax] RDB Question

[Jan-Erik Söderholm]

Den 2018-12-04 kl. 14:26, skrev Arne Vajhøj:
> On 12/3/2018 11:10 PM, Dave Froble wrote:
>> On 12/3/2018 9:50 PM, Kerry Main wrote:
>>> Also, Rdb supports row level locking which is a pretty big performance
>>> feature that some DB's do not support.
>>
>> Why do we need different names for things.  Not that I've ever used Rdb, 
>> but, isn't that basically the same as a record lock?
> 
> Yes.
> 
>> And without that, I'm not sure I'd want to use a RDBMS ....
> 
> It works without.
> 
> Note that we are not talking  functionality of record locking
> vs functionality of no locking.
> 
> We are talking performance impact of database locking rows vs
> performance impact of database locking pages.
> 
> Both support the integrity of the database.
> 
> But in some cases the performance is better if the
> database can lock individual rows instead of locking
> pages (8 KB or whatever chunks).
> 
> Arne
> 

Note also that, even if Rdb supports record locking (has done from
V1.0, if I'm not wrong), it also has something called "Adjustable
record locking". So Rdb doesn't move locks down to the record level
if it doesn't have to (row contention between users).

The default is what is shown from this database dump below.
So one single process doing a large query on its own will put
locks at blocks of 1000 database pages at a time (to start with).


$ rmu/dump/head=lock xxxxxxxx
*---------------------------------------------------
* Oracle Rdb V7.3-300         4-DEC-2018 15:38:20.69
*
* Dump of Database header
*     Database: DB_ROOT:[RDB]xxxxxx.RDB;1
*
*---------------------------------------------------

Database Parameters:
     Root filename is "DB_ROOT:[RDB]xxxxxxxx.RDB;1"
     Locking...
       - Adjustable record locking is enabled
           Fanout factor 1 is 10 (10 pages)
           Fanout factor 2 is 10 (100 pages)
           Fanout factor 3 is 10 (1000 pages)
       - Carry-over lock optimization is enabled
       - Lock tree partitioning is disabled
$

You can get all sorts of statistics from the Rdb “show stat” page.
You want the “timeout” and “deadlocks” to be low, of course…


statistic......... rate.per.second........ total...... average..
name.............. max.... cur... avg..... count...... per.trans
locks requested       2616      0    136.7  1498212727      12.4
  rqsts not queued      710      0     10.1   110878016       0.9
  rqsts stalled           1      0      0.1     1821949       0.0
  rqst timeouts           0      0      0.0          15       0.0
  rqst deadlocks          0      0      0.0          21       0.0
locks promoted         648    174    112.0  1228298204      10.1
  proms not queued       45     18     10.9   120503685       1.0
  proms stalled          61     31     15.1   166502162       1.3
  prom timeouts           0      0      0.0          39       0.0
  prom deadlocks          0      0      0.0          10       0.0
locks demoted          694    154    147.9  1620781031      13.4
locks released        1905      0    126.1  1382032251      11.4
blocking ASTs           99     48     24.9   272962448       2.2
stall time x1000      7239     47     31.1   341033144       2.8
invalid lock block       0      0      0.0        9811       0.0
ignored lock mode        0      0      0.0           0       0.0