Htmldb_collection and db read

Question

Is there a way to force sequential read over scattered read when using htmldb_collection.add_member?
I have traced an issue with response time to the following section of my code:
if length(dcg) > 1 then
          htmldb_collection.add_member(
               p_collection_name => 'DCGCOLLECTION',
               p_c001 => shuttle_rec.obt_seq_id,
               p_c002 => dcg,
               p_generate_md5 => 'NO');
end if;
Here is what I am seeing in TKPROF (sorry I can not get the execution report section formatted better). I attempted to recreate the same flow each time, but because I can not predict when the different reads will happen it is difficult. Therefore I have cut and pasted the corresponding sections of the two trace and tkprof output files below.
You will see that when the system responds as desired, it is using “INDEX RANGE SCAN WWV_FLOW_COLLECTION_MEMBERS_PK” and “db file sequential read”. When response time is slow it uses “INDEX FAST FULL SCAN WWV_FLOW_COLLECTION_MEMBERS_PK” and “db file scattered read”.
FAST RESPONSE:
TRACE FILE – just enough to show the collection name (value=)
SELECT NVL(MAX(SEQ_ID),0) MAXSEQ FROM WWV_FLOW_COLLECTIONS$ C, WWV_FLOW_COLLECTION_MEMBERS$ M WHERE C.SESSION_ID = V('SESSION') AND C.USER_ID = :B4 AND C.SECURITY_GROUP_ID = :B3 AND C.FLOW_ID = :B2 AND C.ID = M.COLLECTION_ID AND C.COLLECTION_NAME = UPPER(:B1 )
END OF STMT
PARSE #53:c=0,e=81,p=0,cr=0,cu=0,mis=0,r=0,dep=2,og=1,tim=4046522821
BINDS #53:
bind 0: dty=1 mxl=2000(255) mal=00 scl=00 pre=00 oacflg=03 oacfl2=206001 size=2080 offset=0
bfp=091722d4 bln=2000 avl=04 flg=05
value="RICH"
bind 1: dty=2 mxl=22(21) mal=00 scl=00 pre=00 oacflg=03 oacfl2=206001 size=0 offset=2000
bfp=09172aa4 bln=22 avl=09 flg=01
value=1807302131050935
bind 2: dty=2 mxl=22(21) mal=00 scl=00 pre=00 oacflg=03 oacfl2=206001 size=0 offset=2024
bfp=09172abc bln=22 avl=03 flg=01
value=106
bind 3: dty=1 mxl=32(13) mal=00 scl=00 pre=00 oacflg=03 oacfl2=206001 size=0 offset=2048
bfp=09172ad4 bln=32 avl=13 flg=01
value="DCGCOLLECTION"
TKPROF –
SELECT NVL(MAX(SEQ_ID),0) MAXSEQ
FROM
WWV_FLOW_COLLECTIONS$ C, WWV_FLOW_COLLECTION_MEMBERS$ M WHERE C.SESSION_ID =
V('SESSION') AND C.USER_ID = :B4 AND C.SECURITY_GROUP_ID = :B3 AND
C.FLOW_ID = :B2 AND C.ID = M.COLLECTION_ID AND C.COLLECTION_NAME =
UPPER(:B1 )
call count cpu elapsed disk query current rows
Parse 2 0.00 0.00 0 0 0 0
Execute 226 0.03 0.07 0 0 0 0
Fetch 226 0.01 0.03 3 1145 0 226
total 454 0.04 0.10 3 1145 0 226
Misses in library cache during parse: 1
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 67 (recursive depth: 2)
Rows Row Source Operation
2 SORT AGGREGATE (cr=10 pr=3 pw=0 time=18198 us)
0 NESTED LOOPS (cr=10 pr=3 pw=0 time=18167 us)
2 TABLE ACCESS BY INDEX ROWID WWV_FLOW_COLLECTIONS$ (cr=4 pr=0 pw=0 time=277 us)
2 INDEX UNIQUE SCAN WWV_FLOW_COLLECTIONS_UK (cr=2 pr=0 pw=0 time=238 us)(object id 52046)
0 INDEX RANGE SCAN WWV_FLOW_COLLECTION_MEMBERS_PK (cr=6 pr=3 pw=0 time=17876 us)(object id 52050)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
db file sequential read 3 0.00 0.01
INSERT INTO WWV_FLOW_COLLECTION_MEMBERS$( COLLECTION_ID, SEQ_ID, C001, C002,
C003, C004, C005, C006, C007, C008, C009, C010, C011, C012, C013, C014,
C015, C016, C017, C018, C019, C020, C021, C022, C023, C024, C025, C026,
C027, C028, C029, C030, C031, C032, C033, C034, C035, C036, C037, C038,
C039, C040, C041, C042, C043, C044, C045, C046, C047, C048, C049, C050,
MD5_ORIGINAL )
VALUES
( :B53 , :B52 , :B51 , :B50 , :B49 , :B48 , :B47 , :B46 , :B45 , :B44 , :B43 ,
:B42 , :B41 , :B40 , :B39 , :B38 , :B37 , :B36 , :B35 , :B34 , :B33 , :B32
, :B31 , :B30 , :B29 , :B28 , :B27 , :B26 , :B25 , :B24 , :B23 , :B22 ,
:B21 , :B20 , :B19 , :B18 , :B17 , :B16 , :B15 , :B14 , :B13 , :B12 , :B11 ,
:B10 , :B9 , :B8 , :B7 , :B6 , :B5 , :B4 , :B3 , :B2 , :B1 )
call count cpu elapsed disk query current rows
Parse 1 0.01 0.00 0 0 0 0
Execute 59 0.12 0.12 7 30 311 59
Fetch 0 0.00 0.00 0 0 0 0
total 60 0.14 0.13 7 30 311 59
Misses in library cache during parse: 1
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 67 (recursive depth: 2)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
db file sequential read 6 0.00 0.02
UPDATE WWV_FLOW_COLLECTIONS$ SET COLLECTION_CHANGED = 'Y'
WHERE
ID = :B1 AND COLLECTION_CHANGED = 'N'
call count cpu elapsed disk query current rows
Parse 2 0.01 0.00 0 0 0 0
Execute 226 0.01 0.02 0 452 18 6
Fetch 0 0.00 0.00 0 0 0 0
total 228 0.03 0.03 0 452 18 6
Misses in library cache during parse: 1
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 67 (recursive depth: 2)
Rows Row Source Operation
2 UPDATE (cr=4 pr=0 pw=0 time=476 us)
2 TABLE ACCESS BY INDEX ROWID WWV_FLOW_COLLECTIONS$ (cr=4 pr=0 pw=0 time=66 us)
2 INDEX UNIQUE SCAN WWV_FLOW_COLLECTIONS_PK (cr=2 pr=0 pw=0 time=38 us)(object id 52045)
SLOW RESPONSE:
TRACE FILE – just enough to show the collection name (value=)
SELECT NVL(MAX(SEQ_ID),0) MAXSEQ FROM WWV_FLOW_COLLECTIONS$ C, WWV_FLOW_COLLECTION_MEMBERS$ M WHERE C.SESSION_ID = V('SESSION') AND C.USER_ID = :B4 AND C.SECURITY_GROUP_ID = :B3 AND C.FLOW_ID = :B2 AND C.ID = M.COLLECTION_ID AND C.COLLECTION_NAME = UPPER(:B1 )
END OF STMT
PARSE #39:c=0,e=89,p=0,cr=0,cu=0,mis=0,r=0,dep=2,og=1,tim=1298905691
BINDS #39:
bind 0: dty=1 mxl=2000(255) mal=00 scl=00 pre=00 oacflg=03 oacfl2=206001 size=2080 offset=0
bfp=06250cb8 bln=2000 avl=04 flg=05
value="RICH"
bind 1: dty=2 mxl=22(21) mal=00 scl=00 pre=00 oacflg=03 oacfl2=206001 size=0 offset=2000
bfp=06251488 bln=22 avl=09 flg=01
value=1807302131050935
bind 2: dty=2 mxl=22(21) mal=00 scl=00 pre=00 oacflg=03 oacfl2=206001 size=0 offset=2024
bfp=062514a0 bln=22 avl=03 flg=01
value=106
bind 3: dty=1 mxl=32(13) mal=00 scl=00 pre=00 oacflg=03 oacfl2=206001 size=0 offset=2048
bfp=062514b8 bln=32 avl=13 flg=01
value="DCGCOLLECTION"
TKPROF –
SELECT NVL(MAX(SEQ_ID),0) MAXSEQ
FROM
WWV_FLOW_COLLECTIONS$ C, WWV_FLOW_COLLECTION_MEMBERS$ M WHERE C.SESSION_ID =
V('SESSION') AND C.USER_ID = :B4 AND C.SECURITY_GROUP_ID = :B3 AND
C.FLOW_ID = :B2 AND C.ID = M.COLLECTION_ID AND C.COLLECTION_NAME =
UPPER(:B1 )
call count cpu elapsed disk query current rows
Parse 1 0.00 0.00 0 0 0 0
Execute 224 0.10 0.06 0 0 0 0
Fetch 224 32.37 603.54 1916959 1923042 0 224
total 449 32.48 603.61 1916959 1923042 0 224
Misses in library cache during parse: 0
Optimizer mode: ALL_ROWS
Parsing user id: 67 (recursive depth: 2)
Rows Row Source Operation
224 SORT AGGREGATE (cr=1923042 pr=1916959 pw=0 time=603553959 us)
6160 NESTED LOOPS (cr=1923042 pr=1916959 pw=0 time=73040535 us)
224 TABLE ACCESS BY INDEX ROWID WWV_FLOW_COLLECTIONS$ (cr=448 pr=0 pw=0 time=21810 us)
224 INDEX UNIQUE SCAN WWV_FLOW_COLLECTIONS_UK (cr=224 pr=0 pw=0 time=18572 us)(object id 52046)
6160 INDEX FAST FULL SCAN WWV_FLOW_COLLECTION_MEMBERS_PK (cr=1922594 pr=1916959 pw=0 time=73009271 us)(object id 52050)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
db file scattered read 124352 0.03 588.32
INSERT INTO WWV_FLOW_COLLECTION_MEMBERS$( COLLECTION_ID, SEQ_ID, C001, C002,
C003, C004, C005, C006, C007, C008, C009, C010, C011, C012, C013, C014,
C015, C016, C017, C018, C019, C020, C021, C022, C023, C024, C025, C026,
C027, C028, C029, C030, C031, C032, C033, C034, C035, C036, C037, C038,
C039, C040, C041, C042, C043, C044, C045, C046, C047, C048, C049, C050,
CLOB001, MD5_ORIGINAL )
VALUES
( :B54 , :B53 , :B52 , :B51 , :B50 , :B49 , :B48 , :B47 , :B46 , :B45 , :B44 ,
:B43 , :B42 , :B41 , :B40 , :B39 , :B38 , :B37 , :B36 , :B35 , :B34 , :B33
, :B32 , :B31 , :B30 , :B29 , :B28 , :B27 , :B26 , :B25 , :B24 , :B23 ,
:B22 , :B21 , :B20 , :B19 , :B18 , :B17 , :B16 , :B15 , :B14 , :B13 , :B12 ,
:B11 , :B10 , :B9 , :B8 , :B7 , :B6 , :B5 , :B4 , :B3 , :B2 , :B1 )
call count cpu elapsed disk query current rows
Parse 1 0.00 0.00 0 0 0 0
Execute 224 0.39 0.57 190 11 1319 224
Fetch 0 0.00 0.00 0 0 0 0
total 225 0.39 0.57 190 11 1319 224
Misses in library cache during parse: 1
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 67 (recursive depth: 2)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
db file sequential read 188 0.00 0.06
UPDATE WWV_FLOW_COLLECTIONS$ SET COLLECTION_CHANGED = 'Y'
WHERE
ID = :B1 AND COLLECTION_CHANGED = 'N'
call count cpu elapsed disk query current rows
Parse 1 0.00 0.00 0 0 0 0
Execute 224 0.01 0.03 0 448 12 4
Fetch 0 0.00 0.00 0 0 0 0
total 225 0.01 0.03 0 448 12 4
Misses in library cache during parse: 0
Optimizer mode: ALL_ROWS
Parsing user id: 67 (recursive depth: 2)
Rows Row Source Operation
4 UPDATE (cr=448 pr=0 pw=0 time=9004 us)
4 TABLE ACCESS BY INDEX ROWID WWV_FLOW_COLLECTIONS$ (cr=448 pr=0 pw=0 time=7205 us)
224 INDEX UNIQUE SCAN WWV_FLOW_COLLECTIONS_PK (cr=224 pr=0 pw=0 time=4003 us)(object id 52045)
Thanks for any help.

Answer 1

Vikas,
     pga_aggregate_target = 25165824
     workarea_size_policy = AUTO
I have not run statistics on all tables in my development database, so I believe I am operating in Rules Based Optimization.
However, all pages running against tables in my database operate fine. It is not until I create an htmldb_collection by running a query against another htmldb_collection that I see slow response times.
Here is an overview of the process, and the steps I went through when tracing:
User logs in and is brought to the main page.
User selects “Locate Agreements” from a sidebar menu and is sent to a page with reports region built on the AGREEMENTS table (currently 450 rows in development).
User selects “Costa Rica” from a select list of terminating countries and the page is submitted and refreshed showing only Costa Rica agreements.
User clicks on the ‘Edit’ link for an agreement and is sent to the details page for the selected record.
     Now that a specific agreement has been selected, this page fires the on-demand process “load tier collections” on load, after footer. This process is viewable by going to http://htmldb.oracle.com/pls/otn/f?p=23228:2:218044503435049191::::: and downloading. Processing time to this point is fine.
User selects “Tiers” from the sidebar menu and is sent to a page built on the htmldb_collection OBTCOLLECTION which was created by the load tier collections process.
     Here is where the delay occurs. This page fires the on-demand process “load shuttle collections” on load, after footer. This process is viewable by going to http://htmldb.oracle.com/pls/otn/f?p=23228:2:218044503435049191::::: and downloading. This process creates multiple htmldb_collections for use on the next page. Using a cursor to move through the OBTCOLLECTION (created earlier), four fields, each containing semi-colon delimited strings, are parsed and the values are inserted into the appropriate collections (DCGCOLLECTION, CITYCOLLECTION, PRODCOLLECTION, PRDCOLLECTION). It would appear, after looking at the trace files, that the creation of the DCGCOLLECTION is causing the biggest delay. This page will load in seconds when operating correctly, but takes as much as 10 minutes when it is not. I have seen this happen at all times of the day, and there is nothing else (nor anyone else) running on the server.
Richard