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Library cache (PIPES) [message #630061] Fri, 19 December 2014 08:10
mrinouk
Messages: 1
Registered: December 2014
Junior Member
Hi,

In library cache ( V$LIBRARYCACHE ), in namespace pipes, we saw an important increase of "get requests", like this:

snap_id	        NMSPACE Get Requests	PctMiss Pin Requests	PctMiss	Reloads	Invalidations
	Monday							
27869	02:00	PIPE	20 911 881	-0.01	20 913 579	-0.06	0	0
27870	03:00	PIPE	24 829 316	-0.01	24 826 624	-0.07	0	0
	Thursday							
27917	02:00	PIPE	19 255 109	0	19 259 406	-0.05	0	0
27918	03:00	PIPE	19 188 723	0	19 193 793	-0.02	0	0
	Wednesday							
27938	11:00	PIPE	18 002 157	0	18 006 747	-0.04	0	0
27939	12:00	PIPE	13 962 878	0	13 969 177	-0.02	0	0
27940	01:00	PIPE	19 249 281	-0.01	19 248 737	-0.07	0	0
27941	02:00	PIPE	20 435 226	0	20 442 743	-0.02	0	0
27942	03:00	PIPE	51 165 927	-0.03	51 197 427	-0.18	0	0
27943	04:00	PIPE	45 672 194	-0.04	45 671 420	-0.13	0	0
27944	05:00	PIPE	17 585 814	-0.01	17 587 560	-0.06	0	0
	Tuesday							
27961	10:00	PIPE	91 752 387	-0.11	91 712 252	-0.36	0	0  <==== trouble is starting
27962	11:00	PIPE	52 305 928	-0.05	52 343 249	-0.2	0	0
27963	12:00	PIPE	30 467 272	-0.01	30 517 823	-0.16	0	0
27964	01:00	PIPE	82 386 796	-0.08	82 442 692	-0.29	0	0
27965	02:00	PIPE	114 636 849	-0.48	114 258 737	-1.05	0	0
27966	03:00	PIPE	74 339 924	-0.03	74 315 143	-0.2	0	0
	Monday							
28037	02:00	PIPE	505 887 190	-1.34	499 378 548	-3.27	0	0
28038	03:00	PIPE	599 214 887	-0.81	595 138 484	-2.15	0	0
	Thursday							
28061	02:00	PIPE	357 479 212	-0.73	354 683 831	-1.98	0	0
28062	03:00	PIPE	433 623 388	-1.28	425 918 611	-3.2	0	0



Load wasn't changed during that time, it was same as usual, but programs that were using DBMS_PIPES were very slow.

We had to restart Oracle DB in order to have "get requests" normal values (around 20 millions) and to recover performance of DBMS_PIPES.

My question is the following: what do you think it may cause this ? In fact, I'm trying to understand the true meaning of "Get Requests" for the namespace PIPES ? What do it does ?

Thanks!

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