From these symptoms, I conclude something wrong with the integration between Lazarus and Oracle client.
Googled one article says, 11g client is buggy, while 12c works better. As such, I upgraded my oracle client from 11.2.0.1 to 11.2.0.4 to prevent this issue. (No time to verify his finding)
From some more articles related to install Oracle InstantClient, I realize the environment variable LD_LIBRARY_PATH is the key to tell Lazarus where to find the relevant library file like oci.dll.
I compared and found oci.dll is under $ORACLE_HOME/bin, (surprisingly not $ORACLE_HOME/lib ), thus I set LD_LIBRARY_PATH to the bin directory. with this setting I see no more missing oci.dll message.
Next, I follow the same article to continue fixing the missing TOracleConnection component. step1, 2, 3, compiling ... , restart IDE, Finally I see the icon there.
Big Thanks to Sebastian Folz, M. Sc.
Here, add some more info related to his step 3.
Step 3: Enabling the TOracleConnection in your Lazarus installation again. You have to go to the "Package" menu entry. Select "Open loaded Package". In the dialog you select the package "sqldblaz". Now click "add" and go to the tab "Add files". Then browse to the file "oracleconnection.pp" under "[Lazarus directory]\fpc\2.6.2\source\packages\fcl-db\src\sqldb\oracle" and add it to the package. The next step is, to change the file "registersqldb". Search for the first occurence of
{$DEFINE HASORACLECONNECTION}
It's in an {$IFNDEF WIN64} section. You need to move it out there. I moved it under the line
{$DEFINE HASSYBASECONNECTION}
. Then save the file, compile the package via "compile" button. If it compiled successfully, click the button "use" and then "install". Now your Lazarus should be build new. After strating the IDE again,
The registersqldb is D:\lazarus64\components\sqldb\registersqldb.pas, and my modification to file as shown in the screenshot.
