How much space is required in rim directory to hold captured data when target is shutdown. (4330676)

How much space is required in rim directory to hold captured data when target is shutdown.

When Shareplex or database on target is shutdown, the source Shareplex or target Shareplex (in case of latter) will keep gathering changes from source database and this will result in queue buildup on source or target Shareplex respectively.  This will result in rim directory filling up on respective Shareplex instance. Likewise, if a Shareplex process on source is stopped or target, this can result in queue buildup on source or target respectively,  which will need space on the rim directory on the appropriate  Shareplex instance.

Stoppage of Shareplex instance on target or Shareplex processes on source or target will require space on rim directory to hold the data.

The database changes constitute approximately 33% of the redo logs generated. Since Shareplex replicates changes to the source database, and since not all but a subset of tables are replicated, a conservative estimate can be derived. Shareplex rim directory should have the size of approx 33% of the redo generated during the time the Shareplex instance or Shareplex processes are stopped which will result in accumulation of queue data.

For further details please refer to Shareplex Administrator Guide Chapter titled “Planning Shareplex Replication” section titled “Disk space for queue files”.

Shareplex Administrator Guide Chapter titled “Planning Shareplex Replication” section titled “Disk space for queue files" delves on related topic as below: To determine the amount of queue space on each system 1 Use a worst-case scenario and estimate the length of downtime to be tolerated. 2 Determine how much data is replicated in that time, using the following formula as a guide. This formula multiplies the redo log value by one-third because only about one-third of the redo log is actually data that is replicated. The rest is data used by Oracle to maintain and operate the instance itself. [size of a redo log] x [number of log switches in 1 hour] x 1/3 x [number of hours downtime] = amount of disk space needed for the queues on each system Example: Suppose you expect to recover from 8 hours of downtime and your redo logs are 60 MB. They switch five times an hour. According to the formula, you need 800 MB of space on the source machine and on the target machine for the SharePlex queues. [60 MB redo log] x [5 switches/hour] x [1/3] x [8 hours] = 800 MB disk space