Similarly, it is also possible to create multiplexed Redo logs in the Oracle database (multiple copies of Redo log files), also known as transaction logs.
This segment is heavily used when users are querying data at the same time other users are modifying it. UNDO segments allow an Oracle database to capture changes taking place on database blocks and lets the database reconstruct an image of a table record that will point to the state before the modification occurred. It is very common for organizations to allocate tens of gigabytes of storage for UNDO segments. ĭatabase components An Oracle database consists of components such as UNDO segments, which sets it apart from most relational databases.To answer this type of question, the following architectural and implementation differences between Oracle and other databases have to be considered: Read more Navigate Downĭatabase sizing is another important task in any database migration project, and the most common question customers ask concerns how large the Oracle database should be if their Sybase database is 100 GB in size. Therefore, a Sybase database is mapped to an Oracle schema. This is not the case, as Oracle has the concept of schemas (i.e., a database user).
This can cause customers to believe they need to create an Oracle database server for each Sybase database. Oracle, on the other hand, has one database for the entire data engine. It is good to understand the server architecture differences between these two databases however, these differences will not have an adverse effect on your migration project and estimates.Ī key difference is that the Sybase data engine can have multiple databases within one engine. Additional Oracle background processes include the CJQ job queue processor, CQJ0 job queue controller, FMON mapping libraries, LMON locking manager, and MMON collector for AWR (Automatic Workload Repository). In an Oracle Real Application Cluster (RAC), the various ARCH processes can be utilized to ensure that copies of the archived redo logs for each instance are available to the other instances in the RAC setup should they be needed for recovery. The optional ARCH archive process writes filled redo logs to the archive log location(s). There are two processes of the Sybase database server, whereas an Oracle instance has five mandatory processes: SMON (System Monitor), PMON (Process Monitor), LGWR (Log Writer), DBWR (Database Writer), and CKPT (Checkpoint).
Sybase database servers consist of a data server and a backup server. Tom Laszewski, Prakash Nauduri, in Migrating to the Cloud, 2012 Database Server Sybase Migrations from a Systems Integrator Perspective, and Case Study
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