Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>My past experience of using oracle LOB type data to store large data has not been good. It is fine when it is under 4k since it store it locally like varchar2. Once it is over 4k, you start seeing performance degrade. Perhaps, things may have improved since I last tried it a couple of years ago, but here are the things I found in the past for your information:</p> <p>As clients need to get LOBs via oracle server, you may consider the following interesting situation.</p> <ul> <li>lob data will compete limited SGA cache with other data type if oracle decide to cache it. As clob data are general big, so it may push other data </li> <li>lob data get poor disk read if oracle decide not to cache it, and stream the data to the client.</li> <li>fragmentation is probably something that you haven't encountered yet. You will see if your applications delete lobs, and oracle tries to reuse the lob. I don't know if oracle support online defragmenting the disk for lob (they have for indexes, but it takes long time when we tried it previous).</li> </ul> <p>You mentioned 4s for 100 lobs of avg 20k, so it's 40ms per lobs. Remember each lob needs to have to retrieved via separate Lob locater (it is not in the result set by default). That is an additional round trip for each lob, I assume (I am not 100% sure on this since it was a while ago) If that is the case, I assume that will be at least 5ms extra time per round trip in serial order, right? If so, your performance is already first limited by sequential lob fetches. You should be able to verify this by tracking the time spent in sql execution vs lob content fetching. Or you can verify this by excluding the lob column as suggested by the previous answer in the post, which should tell you if it is lob related.</p> <p>Good luck </p>
    singulars
    1. This table or related slice is empty.
    1. POOracle CLOB performance
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USOscar Chan
    1. USOscar Chan
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. This table or related slice is empty.
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload