I need to load large amount of data on a table in DB2 database. I am using CLI load mode on a table written in C using SQLSetStmtAttr function. Select statements does not work (the table gets locked) when it is set.
When the loading of the data completes I am doing load mode off. After that the table becomes accessible so that i can perform select from db2 command line tools (or control center).
But the problem is when my C program crashes or fails before doing load mode off. The table is always locked. I have to drop the table and all previous data is lost.
My question is whether there is a way to recover the table?
DBMS Documentation is your friend. You can read the description of SQL0668N (or any other error!) to find out what reason code 3 means, as well as how to fix it.
Basically, when a LOAD operation fails, you need to perform some cleanup on the table – either restart or terminate it. This can be done using the LOAD utility from outside of your program (e.g., LOAD from /dev/null of del TERMINATE into yourtable nonrecoverable) but you can also do it programatically.
Typically you would do this using the db2Load() API, and setting the piLongActionString member of the db2LoadStruct parameter you pass to db2Load(), with the same RESTART or TERMINATE operation.
It looks like you can set the SQL_ATTR_LOAD_INFO statement to the same db2LoadStruct when using a CLI Load, too, but I am not sure if this would actually work to complete a load restart / terminate.
Related
I've had a strange bug pop up -- when I write to a partitioned table, then immediately after do a select on that same table, I get an error like:
./2018.04.23/ngbarx/cunadj. OS reports: Operation not permitted.
This error does not appear if, after writing the table, I wait a few seconds. This to me seems like pointing towards there being a caching situation, where q responds before an operation is complete, but afaik everything I am doing should be synchronous.
I would love to understand what I am doing wrong / what is causing this error exactly / which commands are executing asynchronously.
The horrible details:
Am writing from Python connected to q synchronously using the qpython3 package
The q session is launched with slaves i.e. -s 4
To write the partitioned table, I am using the unofficial function .Q.dcfgnt which can be found here
I write to a q session that was initialized with a database directory as is usual when dealing with partitioned tables
After writing the table with .Q.dcfgnt, but before doing the select, I also do .Q.chk`:/db/; system"l /db/"; .Q.cn table in that order, just to be sure the table is up and ready to use in the q session. These might be both overkill and in the wrong order, but I believe they are all synchronous calls afaik, please correct me if I am wrong.
The trigger to the error is a 10#select from table; I understand
why this is a bad idea to do in general on a partitioned table, but
also from my understanding it shouldn't be triggering the particular error that I am getting.
I have been working on a reporting database in DB2 for a month or so, and I have it setup to a pretty decent degree of what I want. I am however noticing small inconsistencies that I have not been able to work out.
Less important, but still annoying:
1) Users claim it takes two login attempts to connect, first always fails, second is a success. (Is there a recommendation for what to check for this?)
More importantly:
2) Whenever I want to refresh the data (which will be nightly), I have a script that drops and then recreates all of the tables. There are 66 tables, each ranging from 10's of records to just under 100,000 records. The data is not massive and takes about 2 minutes to run all 66 tables.
The issue is that once it says it completed, there is usually at least 3-4 tables that did not load any data in them. So the table is deleted and then created, but is empty. The log shows that the command completed successfully and if I run them independently they populate just fine.
If it helps, 95% of the commands are just CAST functions.
While I am sure I am not doing it the recommended way, is there a reason why a number of my tables are not populating? Are the commands executing too fast? Should I lag the Create after the DROP?
(This is DB2 Express-C 11.1 on Windows 2012 R2, The source DB is remote)
Example of my SQL:
DROP TABLE TEST.TIMESHEET;
CREATE TABLE TEST.TIMESHEET AS (
SELECT NAME00, CAST(TIMESHEET_ID AS INTEGER(34))TIMESHEET_ID ....
.. (for 5-50 more columns)
FROM REMOTE_DB.TIMESHEET
)WITH DATA;
It is possible to configure DB2 to tolerate certain SQL errors in nested table expressions.
https://www.ibm.com/support/knowledgecenter/en/SSEPGG_11.5.0/com.ibm.data.fluidquery.doc/topics/iiyfqetnint.html
When the federated server encounters an allowable error, the server allows the error and continues processing the remainder of the query rather than returning an error for the entire query. The result set that the federated server returns can be a partial or an empty result.
However, I assume that your REMOTE_DB.TIMESHEET is simply a nickname, and not a view with nested table expressions, and so any errors when pulling data from the source should be surfaced by DB2. Taking a look at the db2diag.log is likely the way to go - you might even be hitting a Db2 issue.
It might be useful to change your script to TRUNCATE and INSERT into your local tables and see if that helps avoid the issue.
As you say you are maybe not doing things the most efficient way. You could consider using cache tables to take a periodic copy of your remote data https://www.ibm.com/support/knowledgecenter/en/SSEPGG_11.5.0/com.ibm.data.fluidquery.doc/topics/iiyvfed_tuning_cachetbls.html
I have a .csv file, comma-delimited (located at C:/). I am using the DB2 LOAD utility to load data present in the CSV file in a DB2 table.
LOAD CLIENT FROM C:\Users\somepath\FileName.csv of del
MODIFIED BY NOCHARDEL COLDEL, insert into SchemaName.TABLE_NAME;
CSV file has 25 rows. After the utility completed I got an error message for NOCHARDEL. My table has all 25 rows properly loaded. Now when I try to execute an insert/update/delete statement on any of the tables present in that schema I am getting following error.
Lookup Error - DB2 Database Error: ERROR [55039] [IBM][DB2/AIX64] SQL0290N Table space access is not allowed.
Could you please help me whether I am making any mistake or missing a parameter that is causing lock on the table.
Earlier while loading the file similar situation occurred, where DBA confirmed that Table space in question is in “load in progress” state
Changes generated by the DB2 LOAD utility are not logged (one of the side-effects of its high performance). If the database crashes immediately after the load it will be impossible to recover the table that was loaded by replaying log records, because there are no such records. For this reason the tablespace containing the loaded table is automatically placed in the BACKUP PENDING mode, forcing you to take a backup of that tablespace or the entire database to ensure it is fully recoverable.
There are options that you can specify for the LOAD command that can help you avoid this situation in the future:
NONRECOVERABLE -- this option does not place the tablespace into the BACKUP PENDING mode, but, as its name implies, the table you're loading to becomes non-recoverable in case of a crash, and your only option in that situation will be to drop and re-create the table.
COPY YES -- this option creates a copy of the table prior to loading, which can be used to recover the table to its pre-LOAD state in case of a crash.
If you are only loading 25 records, I suggest you use the IMPORT utility instead -- it does not have these restrictions because it is fully logged (at the price of lower performance, which for 25 records won't matter).
Thanks #mustaccio. I had 60 Million rows to insert. I was using 25 as sample to check the outcome.
To add another point, we later came to know that this is a known DB2 bug that keeps the load in progress state (DB2 is unable to acknowledge that the load has completed and the session remains open indefinitely) and place the table space in backup pending state.
Recovery is the only option to release the table space once it is in pending state.
This issue is fixed in fix pack 10 as per the DB2 team (we are yet to deploy and test). Mean while NONRECOVERABLE key word is working fine for us
The reason why your table is stuck in the LOAD IN PROGRESS state is the NOCHARDEL error happening at the end of the LOAD.
Have you tried restarting the database? This should reinitialize all table spaces and remove any rogue states.
http://www-01.ibm.com/support/docview.wss?uid=swg1IC65395
http://www-01.ibm.com/support/docview.wss?uid=swg21427102
For a mandatory assignment of a DB2 class I'm asked to write o procedure to export "export information about all xxx, delete all xxx and import the information again." where xxx is my table.
This procedure has to be as efficiently as possible.
I'm quite stuck here, quite naively I see two options
1) write a select * from xxx; drop ...; insert; using python or something
2) using some export/import utility of db2
But I can be totally wrong, suggestions?
what I've noticed is that there are not integrity constraints.
You can do that via "export/load/set integrity". I think it is the best way if you execute that in the server.
If you use python, you will have to use a odbc driver or similar to get the data, processes, etc.
If you use python just to execute the commands, it is ok, finally, it is just a call to the database.
If you execute the process in other machine, the net use is increased, and the performance is lower.
Using import, it is just like an "insert" per row in the file which uses a lot of transaction log. Instead, the load command, puts the data diretly in the tablespace and then check the referential integrity (faster process)
Finally, if you want to extract the information very fast, you can buy the IBM InfoSphere® Optim™ High Performance Unload for DB2 for Linux, UNIX and Windows
I have had a similar task before.
The solution is simple and sweet:
A simple export to csv; and once the data has been exported, the main thing is to TRUNCATE the table with your logs being disabled and then load the data back into the table.
EXPORT TO <FileName>.CSV OF DEL SELECT * FROM <TableName>;
ALTER TABLE <TableName> ACTIVATE NOT LOGGED INITIALLY WITH EMPTY TABLE;
LOAD FROM "./<FileName>.CSV" OF DEL INSERT INTO <TableName>;
Recently I implemented a cache component in my iPhone app, that uses SQLite.
I'm writing and reading the data natively w/o any wrapper framework.
The problem is that after using the app for a while it's beginning to get SQLITE_CORRUPT status code in response to a any SQL statement I perform in the DB.
I'm using SQLiteManager as my DB mgmt tool. When the DB becomes corrupted I'm trying to analyze and inspect via the SQLiteManager but it doesn't even allow me to browse through the data in the table and just outputs a laconic message that says data is corrupted.
Anyone can assist with this one ? First of all - How the hell the DB gets to that situation and second - how or where can I see the data anyway ?
Thanks,
Guy.
You can refer this official documentation. Here they have mentioned there are very few chances for db to be corrupted.
They have also list out the chances how DB can be corrupted. And from there refer following example which can cause the problem to the db.
CREATE TABLE ex1(a INTEGER PRIMARY KEY, b);
INSERT INTO ex1 VALUES(1,2);
INSERT INTO ex1 VALUES(2,3);
CREATE TRIGGER ex1_tr1 AFTER UPDATE ON ex1 BEGIN
DELETE FROM ex1 WHERE a=old.b;
END;
UPDATE ex1 SET b=b+1;
In the example above, the first cycle of the UPDATE causes the trigger to fire and delete the second row of the ex1 table. When the second cycle of the UPDATE loop runs, it attempts to process the second row of the ex1 table. SQLite recognized that the second row had been deleted so it aborts the second cycle, but it was failing to clean up after itself properly which could lead to database corruption on subsequent cycles of the loop.
So, Basically you need to find out the situation where this has happened in your code, By debugging or by following steps through your application or any other mechanism.