### Understand the alert

This alert monitors the PostgreSQL table cache hit ratio, which is the percentage of database read requests that can be served from the cache without requiring I/O operations. If you receive this alert, it means your PostgreSQL table cache hit ratio is too low, indicating performance issues with the database.

### What does PostgreSQL table cache hit ratio mean?

The PostgreSQL table cache hit ratio is an important metric for analyzing the performance of a database. A high cache hit ratio means that most read requests are being served from the cache, reducing the need for disk I/O operations and improving overall database performance. On the other hand, a low cache hit ratio indicates that more I/O operations are required, which can lead to performance degradation.

### Troubleshoot the alert

To address the low cache hit ratio issue, follow these steps:

1. Analyze database performance:

Analyze the database performance to identify potential bottlenecks and areas for optimization. You can use PostgreSQL performance monitoring tools such as `pg_top`, `pg_stat_statements`, and `pg_stat_user_tables` to gather information about query execution, table access patterns, and other performance metrics.

2. Optimize queries:

Review and optimize complex or long-running SQL queries that may be causing performance issues. Utilize PostgreSQL features like `EXPLAIN` and `EXPLAIN ANALYZE` to analyze query execution plans and identify optimization opportunities. Indexing and query optimization can reduce I/O requirements and improve cache hit ratios.

3. Increase shared_buffers:

If you have a dedicated database server with sufficient memory, you can consider increasing the `shared_buffers` in your PostgreSQL configuration. This increases the amount of memory available to the PostgreSQL cache and can help improve cache hit ratios. Before making changes to the configuration, ensure that you analyze the existing memory usage patterns and leave enough free memory for other system processes and caching demands.

4. Monitor cache hit ratios:

Keep monitoring cache hit ratios after making changes to your configuration or optimization efforts. Depending on the results, you may need to adjust further settings, indexes, or queries to optimize database performance.

### Useful resources

1. [Tuning Your PostgreSQL Server](https://www.postgresql.org/docs/current/runtime-config-resource.html)