Informatica性能调优(初级)(7)

Informatica性能调优(初级)

inherently slow (as of: 1/1/2000). Hopefully Informatica will speed this up in the future. The external module which exhibits speed problems is the regular expression module (Unix: Sun Solaris E450, 4 CPU's 2 GIGS RAM, Oracle 8i and Informatica). It broke speed from 1500+ rows per second without the module - to 486 rows per second with the module. No other sessions were running. (This was a SPECIFIC case - with a SPECIFIC map - it's not like this for all maps).

5. Remember that Informatica suggests that each session takes roughly 1 to 1 1/2 CPU's. In keeping with this - Informatica play's well with RDBMS engines on the same machine, but does NOT get along (performance wise) with ANY other engine (reporting engine, java engine, OLAP engine, java virtual machine, etc...)

6. Remove any database based sequence generators. This requires a wrapper function / stored procedure call. Utilizing these stored procedures has caused performance to drop by a factor of 3 times. This slowness is not easily debugged - it can only be spotted in the Write Throughput column. Copy the map, replace the stored proc call with an internal sequence generator for a test run - this is how fast you COULD run your map. If you must use a database generated sequence number, then follow the instructions for the staging table usage. If you're dealing with GIG's or Terabytes of information - this should save you lot's of hours tuning. IF YOU MUST - have a shared sequence generator, then build a staging table from the flat file, add a SEQUENCE ID column, and call a POST TARGET LOAD stored procedure to populate that column. Place the post target load procedure in to the flat file to staging table load map. A single call to inside the database, followed by a batch operation to assign sequences is the fastest method for utilizing shared sequence generators.

7. TURN OFF VERBOSE LOGGING. The session log has a tremendous impact on the overall performance of the map. Force over-ride in the session, setting it to NORMAL logging mode. Unfortunately the logging mechanism is not "parallel" in the internal core, it is embedded directly in to the operations.

8. Turn off 'collect performance statistics'. This also has an impact - although minimal at times - it writes a series of performance data to the performance log. Removing this operation reduces reliance on the flat file operations. However, it may be necessary to have this turned on DURING your tuning exercise. It can reveal a lot about the speed of the reader, and writer threads.

9. If your source is a flat file - utilize a staging table (see the staging table slides in the presentations section of this web site). This way - you can also use SQL*Loader, BCP, or some other database Bulk-Load utility. Place basic logic in the source load map, remove all potential lookups from the code. At this point - if your reader is slow, then check two things: 1) if you have an item in your registry or configuration file which sets the "ThrottleReader" to a specific maximum number of blocks, it will limit your read throughput (this only needs to be set if the sessions have a demonstrated problems with constraint based loads) 2) Move the flat file to local internal disk (if at all possible). Try not to read a file across the network, or from a RAID device. Most RAID array's are fast, but Informatica seems to top out, where internal disk continues to be much faster. Here - a link will NOT work to increase speed - it must be the full file itself - stored locally.

10. Try to eliminate the use of non-cached lookups. By issuing a non-cached lookup, you're performance will be impacted significantly. Particularly if the lookup table is also a "growing" or "updated" target table - this generally means the indexes are changing during operation, and the

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