List of Environment Variables in DataStage

General Job Administration

APT_CHECKPOINT_DIR
APT_CLOBBER_OUTPUT
APT_CONFIG_FILE
APT_DISABLE_COMBINATION
APT_EXECUTION_MODE
APT_ORCHHOME
APT_STARTUP_SCRIPT
APT_NO_STARTUP_SCRIPT
APT_STARTUP_STATUS
APT_THIN_SCORE

Buffering in DataStage

Buffering is a technique used in the Datastage jobs to ensure a constant and uninterrupted flow of data to and from stages in such a way that there is no potential dead lock or any fork join problems. It is been implemented in Datastage keeping in mind the fact that the data has to keep moving in the process with an optimized use of the memory in the server. As mentioned by IBM the ideal scenario is when the data flows through the stages without being written on the disk. As in the case of buffering in any system, the upstream operators should to wait for the downstream operators to consume their input before starting to create their records. This is the intention in Datastage too.

Oracle Interview Questions - Part-3

51. What is a database instance? Explain.
A database instance (Server) is a set of memory structure and background processes that access a set of database files. The processes can be shared by all of the users. The memory structure that is used to store the most queried data from database. This helps up to improve database performance by decreasing the amount of I/O performed against data file.

52. What is Parallel Server?
Multiple instances accessing the same database (only in multi-CPU environments)

DataStage Environment variables

1 Buffering	2 Building Custom stages
1.1 APT_BUFFER_FREE_RUN	2.1 DS_OPERATOR_BUILDOP_DIR
1.2 APT_BUFFER_MAXIMUM_MEMORY	2.2 OSH_BUILDOP_CODE
1.3 APT_BUFFER_MAXIMUM_TIMEOUT	2.3 OSH_BUILDOP_HEADER
1.4 APT_BUFFER_DISK_WRITE_INCREMENT	2.4 OSH_BUILDOP_OBJECT
1.5 APT_BUFFERING_POLICY	2.5 OSH_BUILDOP_XLC_BIN
1.6 APT_SHARED_MEMORY_BUFFERS	2.6 OSH_CBUILDOP_XLC_BIN

Input/Output data buffering (on Link) in DataStage

To improve performance and resolve bottlenecks, you can specify how input and output data is buffered. Although the size and operation of the buffer are usually the same for all links on all stages, you can modify the settings for specific links.

By default, data is buffered so that no deadlocks occur. Be careful when changing data buffering settings because specifying inappropriate values might create a deadlock.

Any changes that you make to the properties on the Advanced tab are automatically reflected on the Advanced tab of the stage at the other end of the link.