Re: Db2 and clob columns

Since g_clob_data is CHAR(5242880)

The %LEN(g_clob_data) is always 5242880, so yep you're writing out blanks.

You should use %LEN(i_5000000);

But even there, if the data is passed in with trailing blanks, then yep
you're getting 5MB written out.

A quick fix would be to add OPTIONS(*TRIM) to the parameter, but that would
require a recompile of callers.

You could also add %TRIMR(), but you'd end up doing so twice...

Personally, I'd prefer to ensure the data is trimmed at the origin and then
pass in as CONST instead of VALUE instead of copying the value to the stack.
Also, I'd define g_clob as STATIC, to keep from having it created and
deleted (and INZ) for every call.

I might take a boots and suspenders approach, including a %TRIMR() ... if
the data is already trimmed it should be a no-op.

dcl-pi
i_5000000 varchar(5242880) CONST;
end-pi;

dcl-s g_clob sqltype(clob:5242880) static;

g_clob_data = %TRIMR(i_5000000);
g_clob_len = %len(%TRIMR(i_5000000));

insert into table(myClob)
values (:g_clob);


Charles


On Tue, Apr 16, 2024 at 7:38 AM Jay Vaughn <jeffersonvaughn@xxxxxxxxx>
wrote:

we have a procedure...

dcl-pi
i_5000000 varchar(5242880) value;
end-pi;

dcl-s g_clob sqltype(clob:5242880) inz;

g_clob_data = i_5000000;
g_clob_len = %len(g_clob_data);

insert into table(myClob)
values (:g_clob);


thoughts?

Jay







On Tue, Apr 16, 2024 at 9:31 AM Charles Wilt <charles.wilt@xxxxxxxxx>
wrote:

If you have RPG code writing out the table, I'd look there first.

Make sure the RPG code is properly handling the varchar data.

Charles

On Tue, Apr 16, 2024 at 7:00 AM Jay Vaughn <jeffersonvaughn@xxxxxxxxx>
wrote:

So Charles,

We have a table developed to hold a request clob (5mb) and a response

clob

(5mb) ONLY for storage and auditing purposes.
Not to run queries against.

We have been finding out that some off platform load tests are being
performed and even though the api calls to put rows in this table

should

have 1mb or less requests/responses, we are maxing out the DASD on that
test box and this table ends up with 821G of data.

Again our requests/responses should be well under 1mb each.

So is this table just a bad idea or are we simply over dominating the

box

with our load test volume?

Next time this happens I really want to look at the rows and see what

these

columns have in them.

thanks

Jay








On Mon, Apr 15, 2024 at 6:51 PM Jay Vaughn <jeffersonvaughn@xxxxxxxxx>
wrote:

Thanks Charles.

I’lllook into the allocate but big relief on the storage concern.

Jay

On Apr 15, 2024, at 5:44 PM, Charles Wilt <charles.wilt@xxxxxxxxx>

wrote:

Nope...

variable length data is stored in the overflow section of the

table...

Downside of that is that when you read the row, it takes 2 I/Os.

One

for

the row space and one for the overflow.

If you were mostly writing less that 32k, I'd tell you to take a

look

at

the ALLOCATE clause. That does cause space to be reserved in the

standard

table space. Which wastes space, but then the data only needs 1

I/O

to

be

read.

Charles

On Mon, Apr 15, 2024 at 2:20 PM Jay Vaughn <

jeffersonvaughn@xxxxxxxxx

wrote:

Let’s say I have a table with a 5mb clob column.

Most of my transactions that write to the table mostly consist of

64k

and

less chars written to the clob but we want to reserve the much

higher

storage allocation for when we need it

When the 64k chars are written to that clob on the row, the entire

5mb

of

storage is not written to disk is it??

Tia

Jay

Sent from my iPhone
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