Re: how to identify queries using BLCed tables with the intention of throttling them in TASM.
Note that within a table, some data blocks / logical cylinders may have BLC while others do not. Even if you defined all your tables with BLOCKCOMPRESSION ALWAYS / NEVER, that information is not available in TASM. You'd have to adopt some naming convention (e.g. prefix / suffix indicating BLC) that could be used in a TASM rule.
It depends. For example, BLC tends to be a better choice for infrequently accessed data, and a poorer choice for frequently updated data. SoTemperature-Based BLC, especially when combined with partitioning, can be very useful (and one of the main reasons why you might have tables with a mix of compressed & uncompressed data blocks). But based on your platform characteristics (available CPU capacity, I/O bandwidth, storage capacity), you may sometimes be better off with BLC on nearly everything or on nothing at all.
For an existing table, use the ferret utility. Or create a new table and copy the data (setting table attributes and/or query band appropriately to prevent compression).