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The after-imaging feature lets you recover a database that was damaged when a failure caused the loss of the database or primary recovery (before image) area. When you enable after-imaging, the database engine writes notes containing a description of all database changes to the after-image (AI) files. The AI files with the roll-forward recovery process can be used to restore the database to the condition it was in before the database was lost, without losing completed transactions that occurred since the last backup. If the After-image files are not written with the changes to the database changes then and there, a considerable amount of data may be lost and hence, the database cannot be recovered completely. Also, if the buffer is not available on the after-image file, then, the processes that are initiating the writes on the file may be made to wait for a longer duration. This may also result in an increase in the wait time of the physical I/O on the file and eventual data loss if the database fails during the waiting period of the processes. Therefore, it is necessary to maintain a close watch on the writes to the AI file. The ProAILogActTest test helps administrators in monitoring the writes on the AI file.

By constantly monitoring the writes to the after-image file, this test reports the total number of writes to the file, the writes that were performed by the after-image writer and the number of times a process had to wait for the buffer in the AI file to write etc. This way, administrators can determine how well the writes were performed on the AI file and take precautionary steps to avoid data loss completely.

Output of the test : One set of results for every Progress database server that is being monitored.

Measurement	Description	Measurement Unit	Interpretation
Total_writes	Indicates the total number of writes to the after-image file per second during the last measurement period.	Writes/Sec	The value of this measure includes the value of the AIW_writes measure too.
AIW_writes	Indicates the total number of writes performed by the after-image writer per second during the last measurement period.	Writes/Sec
AIW_writes_hit_ratio	Indicates the ratio between the writes performed by the after-image writer and the total writes to the after-image file during the last measurement period.	Percent
Buffer_busy_waits	Indicates the number of times Buffer Busy waits have occurred on the after-image file when a block in the buffer cache was being held by the after-image writer during the last measurement period.	Number	The Buffer Busy wait happens when a session wants to access a database block in the buffer cache but it cannot because the buffer is busy. Another session is modifying the block and the contents of the block are in flux during the modification. The two main cases where this wait can occur are: Another session is reading the block into the buffer Another session holds the buffer in an incompatible mode to our request If too many buffer busy waits occur on the database, then it often indicates that the physical writes to the after-image file is taking longer to complete.
Force_wait	Indicates the rate at which commit waits have occurred on the after- image file when a block in the buffer cache was being held by the After image writer during the last measurement period.	Records/sec
Waits_for_no_buffer	Indicates the number of times a process had to wait since the buffer was not available in the after-image file during the last measurement period.	Number